How does Jake turn from the badass double pistols and a wink guy, to the human equivalent of Tavros?

Okay one, I’m sorry, but Jake has never been badass

He became the “human equivalent of Tavros” only in the last few weeks (in-story time) as his relationship with Dirk began to decline and kept venting to Jane oblivious of how it made her feel. The kicker being (and this all happened in the last 24 hours mind you) when Jane blew up on him, when Dirk broke up with him, and when Heiress Jane told him that he was good for nothing but looking hot and making babies.  Dude’s self-esteem and self-confidence are at an all time low, just like Tavros’s was back in Hivebent. That’s why they get along so well.