“Successful” yes but not among the greatest. Fangio, Surtees, Clark, Senna, among others. Back when F-1 was a blood sport.
And he won the majority of his titles during a time when Mercedes had a super dominant car and the rules basically stopped the other teams from being able to upgrade their cars to catch up. He only had to beat his teammate to be assured the title, and one he year he couldn’t even do THAT.
I place a HUGE asterisk beside most of his championships.