I think it's nonsense to say that voters don't like Khan because he is Muslim and from an ethnic minority. Yes, some people are racist but holding someone to a lower standard because of race/religion is also prejudiced, just in the other direction.
I voted for him but Khan hasn't performed as well as I hoped, there are some major issues that he has not managed to sort out (knife crime, more cycling lanes, air pollution). On the whole, he has been too keen on empty sloganeering instead of real change. I did not care for his BLM New Year's Eve display - really, we're in a fucking pandemic, and all he can think about is virtue-signalling? He must know that some of the BLM aims are pretty controversial. I also thought he is way out of line on trans issues. Not his policy area, very complicated, please shut up and sort out the things you were asked to sort out.
Boris' garden bridge was a disaster, I can only hope that the next Mayor will be better. Will be voting for Shaun Bailey.