Tired of being trounced as a villain? Want to try heroics, just to see what the big deal is? You’re already using a fake name and a costume, just switch up your gimmicks. Who’s going to know? Thus the Masters of Evil are essentially rebranded as the Thunderbolts, a sort of post-Avengers Avengers.
It worked out well for a time. The police stopped shooting at them and they could hide in plain sight while pursuing ulterior goals. The problem, from a villainous perspective, is that heroics became habit-forming because adulation is such a rush. The team eventually purges itself of the faithfully villainous and goes on as a true hero team. More or less.
References: [marvel.com: Thunderbolts]
[wikipedia.org: Thunderbolts]
[marvel.fandom.com: Thunderbolts]
[org]
Metahuman Database 