Very simple. Read any Niall Fergusson book on Empire for the answer why British was best. Also kudos to Britain for the almost completely peaceful dismantling of their empire compared to other European powers. Heres's a starter:
https://www.goodreads.com/book/show/166434.Empire
Also Google many articles (some scholarly) in the folowing vein:
https://www.quora.com/Why-do-the-for...in-or-Portugal
By the way, by the 1930s Empire was certainly a huge economic and military drain on the UK. It was a necessity in terms of global power rather than a money maker. This is beyond question. India of course was still a huge resource, but in return the economic power that is India today is built not only on resources but on centuries of British infrastructure; legal, governmental and hard assets (hospitals/railways, etc.), they had a head start on everything over many of their regional competitors.