He had a plan, a perfect plan even. All it required was Chuuya to cooperate.
Dazai considered that and changed the plan. The only part Chuuya would cooperate with was the one that ended with Chuuya’s fist or foot through the middle of Dazai’s chest, and he wouldn’t fake it, so Dazai would have to think of another way to leave the Mafia and take Chuuya with him.
He didn’t need to drug his partner’s drink, kidnap him, and blow up his car to cover their tracks.
On the plus side, death by Chuuya was still a very real possibility.