Quit India fizzled out in about two months. After Quit India, Gandhi did not launch any movement. Is one to infer that the call to Quit India given in 1942 was acted upon by the British after a lapse of five years in 1947? That there was some kind of an ultra-delayed tubelight response? Quit India call heard after a delay of five years!
Britain hinted at independence in 1946, and announced it formally in 1947, even though there was hardly any pressure from the Congress on Britain to do so. Many of the rulers of the Princely States in fact wondered and questioned the Raj as to why they wanted to leave (they didn’t want them to—it was a question of their power and
perks, which were safe under the British) when there was no movement against them, and no demand or pressure on them to leave.The British initially announced the timeline as June 1948 to leave India.Later, they themselves preponed it to August 1947.

If the British didn’t wish to leave, and it was the Congress which was making them leave, why would the British voluntarily announce preponement of their departure? The long and short of it is that Gandhi and Gandhism and the Gandhian Congress were NOT really the reasons the British left. Gandhi himself  admitted as much.
WHAT THEY SAID What Gandhi had himself said: “I see it as clearly as I see my finger: British are leaving not because of any strength on our part but because of historical conditions and for many other reasons.” — Mahatma Gandhi

S.S. Gill:- “It seems presumptuous to pick holes in Gandhi’s campaigns and strategies, and appear to belittle a man of epic dimensions, especially when the nationalist mythologies render it sacrilegious to re-evaluate his achievements. Great men of action, who perform great deeds, do commit great mistakes. And there is no harm in pointing these out. In one sense it is a Gandhian duty, as he equated truth with God & quot;

Dr BR Ambedkar:- “…The Quit India Campaign turned out to be a complete failure… It was a mad venture and took the most diabolical form. It was a scorch-earth campaign in which the victims of looting, arson and murder were Indians and the perpetrators were Congressmen… Beaten, he [Gandhi] started a fast for twenty-one days in March 1943 while he was in gaol with the object of getting out of it. He failed. Thereafter he fell ill. As he was reported to be sinking the British Government released him for fear that he might die on their hand and bring them ignominy… On coming out of gaol, he [Gandhi] found that he and the Congress had not only missed the bus but had also lost the road. To retrieve the position and win for the Congress the respect of the British Government as a premier party in the country which it had lost by reason of the failure of the campaign that followed up the Quit India Resolution, and the violence which accompanied it, he started negotiating with the Viceroy… Thwarted in that attempt, Mr.Gandhi turned to Mr.Jinnah…”

FREEDOM: THE REAL REASONS

Till the early 1940s the British were well-ensconced in power, and looked forward to comfortably sailing through for several more decades— notwithstanding the Gandhian agitations of over two decades since 1918. If they played politics between the Congress and the Muslim League it was only to prolong their rule, and not to give independence or create Pakistan. They never perceived the Gandhian non-violent methods as threats to their rule. Then what changed that they left? Those major factors are detailed below.
1) WW-II and its Consequence UK’s Precarious Economy, and WW-II Exhaustion.-
1.1- The UK was in a precarious economic condition as a consequence of the Second World War. It was hugely debt- ridden, and the maintenance of its colonies had become a tremendous drag on the UK exchequer. The Britain had colonised India to loot, and not to invest in it or to maintain it. The money flow had to be from India to Britain to justify continuance of the colony; and not the other way round, which had begun to happen

1.2- Militarily, administratively, financially, and above all, mentally the British were too exhausted after the Second World War to continue with their colonies.

2) Netaji Bose, INA and Army Mutinies

2.1) The military onslaught of Netaji Subhas Chandra Bose and his INA hugely shook the British, and the Indian army.
2.2) The Viceroy was shocked to learn of thousands of soldiers of the British-Indian army switching over to INA (to support the enemy nation Japan) after the fall of Singapore in 1942. It meant the Indian soldiers in the British-Indian army could no longer be relied upon. What was more—there was a huge support for Netaji Bose and the INA among the common public in India.

Wrote Maulana Azad in his autobiography: “After the surrender of Japan, the British reoccupied Burma and many officers of the Indian National Army (INA) were taken prisoner. They did not repent their action in having joined the Indian National Army and some of them were now facing trial for treason. All these developments convinced the British that they could no longer rely on the armed forces…”
The British historian Michael Edwardes wrote: “It slowly dawned upon the government of India that the backbone of the British rule, the Indian Army, might now no longer be trustworthy. The ghost of Subhas Bose, like Hamlet’s father, walked the battlements of the Red Fort (where the INA soldiers were being tried), and his suddenly amplified figure overawed the conference that was to lead to Independence.”

The key British decision makers can be listed as under:
1- Lord Clement Attlee, Prime Minister of Great  Britain from August 1945 to 1950. Along with him were Lord Pethick-Lawrence (Secretary of State for India and Burma) and Sir Stafford Cripps (President of the Board of Trade) in London.
2- The Viceroy of India, Field Marshal Viscount Lord Wavell (at the time of the INA trials and Naval mutiny)
3-The last Viceroy of India, Lord Louis Mountbatten (however, the decision to free India had been taken by the time he was appointed. It was his task to implement that decision and actualise time frames).
4-Commander-in-Chief India, General (later, Field Marshal) Claude Auchinleck and his superiors in the Imperial General Staff in London. Communications between them would provide the vital input about the military impact of the INA and subsequent mutinies in the Royal Indian Navy, Air Force and some units of the British Indian Army. This would be the most critical and decisive input.
5- The British Governors of the Indian Provinces and their reports to the Viceroy on the internal situation in the wake of the INA trials also provide clear insights in to the decision-making process and the ground situation in various states in the wake of the INA trials and thenaval mutiny.

Pressure from the US-
The Cripps Mission of March-April 1942, the first one in the direction of freedom for India, was under the pressure from the US. The US felt that the best way to secure India from Japan was to grant it freedom, and obtain its support in the war. US President Roosevelt had constantly pressurised Britain on India, and had specially deputed Colonel Louis Johnson to India as his personal representative to lobby for the Indian freedom.
Gandhi & the Congress?
Gandhi and the Congress were among the minor reasons and nondecisive factors the British left. Strangely, and quite unjustifiably, the focus is on Gandhi, Nehru and the Congress on each anniversary of the Independence Day of India.