I think Khan has done a reasonably fair job as mayor. There has been quite a bit of unsavory criticism that @redalways has mentioned above.
He has also been targeted by the Conservative government who for example pushed him to agree to extend ULEZ in return for funding for TFL when Covid blew a hole through its finances - only then for the Conservatives to use his introduction of the ULEZ expansion as something to berate him for during election time.
Thats similar to the arguments around crime where Johnson as Mayor happily agreed with Treasury to cut police funding in London, leaving Khan to come in and pick up the pieces with less money.
Khan has also come under criticism from some āgreenā campaigners for his support for new tunnels in Silvertown and also, I think extending flights from City Airport.
You canāt keep all the people happy all the time.
Considering the mess he inherited from Bozo, as well as the total lack of support from the Conservative government, Khan has done about as well as can reasonably be expected.
I think Iām more sceptical because Iām not sure how much power the Mayor of London really has. A lot still depends on the largesse of central government. I remember reading quite a fair bit about how TfL was handicapped because the Conservative government couldnāt stnand for having a successful Labour Mayor of London.
This how it seems from the outside. He always seemed reasonable when Iāve heard him speak, and itās a job in which you are bound to upset some people whatever you do.
Iād heard rumours about him years ago that he had questionable behaviour on Trade and Industry events, but this was more along the lines of inappropriate comments along the lines of his fatherās āgaffesā. I do wonder what, exactly, is still to come out about him. It does sound like he had an army of officials sweeping under the carpet behind him.