René Arnoux in 2008
I always liked René Arnoux. Arnoux raced in F1 from '78 till the end of the 1989 season, and while his stock had fallen considerably by the late 80s, it's easy for people today to forget how much he was regarded as a rising star around '79-'81. If I recall correctly he even held the record for most pole positions in one season at one time.
He left the Renault team when they were on top to go drive for Ferrari, presumably seduced by the legend. After two more seasons with Ferrari, the first good, the second somewhat less so, he was canned at the beginning of the third (1985) season after only one start-- and not allowed to drive for anybody else for the rest of the year because the Ferrari people wouldn't release him from his contract. Peering into the psyche of a famous person you've never met is probably silly, but it's difficult not to think that this may have soured him on the sport a bit and hurt his confidence.
After that he spent his last four seasons with Ligier, 1986-'89, and like Arnoux, Ligier didn't have the same form as in the early 80s, especially after their engine supplier (coincidentally, Renault) left F1 at the end of '86 and they had to make do with lesser equipment.