It also didn't help that the British also contuined to ruin their economy during the post-war period as they flip-flopped on whether they should stick to the gold standard or not. Winston Churchill, who had become the "Chancellor of the Exchequer" or what Americans would call the "Treasury Secretary" in 1924, had proposed a return to the Gold Standard in 1925, but then decided to fix it at the pre-war rate instead of the actual current value because his pride refused to accept the reality that the pound sterling had seriously depreciated during the course of the First World War. This was also an utterly disastrous decision that was so bad that the Federal Reserve bank actually had to depress interest rates in the United States and deliberately weaken America’s currency in order to prop up the value of the pound sterling and make it appear that it was stronger than it actually was, and that the dollar hadn't already supplanted it as the new default currency of exchange to keep them afloat. Then, once the Great Depression got underway and the 1931 Crisis was in full effect, they tried to switch off the gold standard again, but it was too little too late and just exacerbated the compounding issues and instability of its crumbling economic stability.
If Churchill is to be blamed for anything regarding destroying the British Empire, then it was for the way he completely fucked up Great Britain's finances and economy during the 1920s and early 1930s, along with setting things up for the Great Depression to even happen in the first place.
Even if the Second World War had been avoided, the position that the British Empire had found itself in by the time of 1939 was the same as the Spanish Empire's fate after the War of the Austrian Succession, in terms of how it would have only taken everything going perfectly, and a level of governmental competence to keep it from being overtaken by its hegemonic rivals while fading into a 'gloroius deterioration'. Much like the Spanish, at first glance, they seemingly held on to all of their colonial holdings, reaching the superficial 'peak' of their Empire and possessed enough power to maintain the glittering facade of being a leading global hegemon; however, it was just the gases escaping from a corpse that had already died yet hadn't realized it yet. The Second World War just cemented this harsh reality even more so and had them going from that 'glorious deterioration' that would have ended up with it having a dignified death postponed to perhaps the 80s and 90s, along with the USSR, to an 'inglorious decomposition' that had it giving up major geopolitical concessions to nations they used to enjoy dictating dictats to with impunity not even a decade prior. Four years of brutal trench warfare just to have them be forced to meet in Washington, D.C. in 1922 to have Yankees dictate Royal Navy policy and decide how many battleships they could build. One of the clearest examples of the spiritual and functional death of their Empire after their "pyrrhic victory" in the First World War.