1. Gets to jump to a title shot. If he fought Stipe and lost, not only does he lose stock, but it wouldn't even be for the title. He's risking his brain cells I exchange for the chance to become a champion.
2. Way more money and fight hype, to be fighting Ngannou former sparring partners.
3. Rule #8482 of MMA prize fighting: No one actually waits until they're actually "ready" to fight someone. The "I'll fight anyone anywhere anytime" mentality has been the downfall of many a UFC fighter. Like those fighters who get their ass beat, ask for an immediate rematch, and get beat up worse than the first time.
Gane struck while the iron was hot and he got himself a title fight.