I assume Brits are about as racist as people everywhere else, so I'm surprised more people aren't drawing a connection between "Tories have a non-white PM" and "Tory electoral coalition fractures as racists flee to Farange's party?"
Their problems started before Sunak, but while Liz Truss was white, she also appointed a black guy with an African-sounding name to be exchequer who was hideously unpopular!
Sunak is a deeply unlikeable candidate for many many many reasons. Perhaps some people didn't vote for him due to his race but I think even in his deeply racist party that was not the reason for his ousting.
An interesting feature of the modern UK Tory Party is that many of their most hardline members of parliament are not white. Notably Suella Braverman and Kemi Badenoch.
he did seem to be mostly trying to appeal to the most racist/bigoted and white section of UK society... kinda setting himself up to be his own first hurdle there.