Tbh, I think no one is really thinking Kizaru is going to win, at least bar 1 or 2 cases. 99% of Admiral fans know Kizaru is going to lose.
They just want him to lose, but to show off and prove, after years of slandering, that an Admiral is indeed about as strong an Emperor. Now, Luffy has beaten Kaido so he is even stronger than the "regular" Emperor, so Kizaru will lose 100%, but what is important is how.
Plus, most like Kizaru and like the work Oda has been doing since the start of his arc, giving him background and all.