They were formed as a supergroup. Clapton had already made his name with The Yardbirds. I don't remember Bruce and Baker's old bands. Clapton of course had the most successful later career. Ginger Baker was the drummer for Blind Faith, another super group that I have to pick a track or two to play. Both Baker and Bruce have passed. Baker was a very odd individual. There is a documentary about him on Netflix, I think, which is worth a watch.