[ Daisy | Kara ] HYDRA destroyed a lot of lives whilst they were hiding inside SHIELD, and a lot of lives after. I'm sorry about your parents. Even if you didn't really get to know them losing them is never easy.
He probably thinks he has nothing left to live for.
Grant probably thinks that is his only choice, he'll want closure or revenge or some mixture of both. Here we realized that going down that path leads to worse things but he doesn't have anyone there to make him see that. HYDRA destroyed him, they destroyed me. He could be trying to dismantle it from the inside. He hates HYDRA as much as he hates SHIELD.