I wasn't convinced of his "innocent slip up" where he forgot fabian was busy. Kuro asked him for questions, and he failed to respond with any. Just looking for every easy lynch going, and saying a lot of nothing to appease you. Essentially, the same reasons that raised red flags for you.
I guessed there was an active mafia, which pinned it down to yourself or Alan. Alan jumping to side with me too the moment I also became active, while making no attempts to reach out to me previously, and stating that you absolutely must be mafia if Kuro wasn't (he knew Kuro wasn't) gave me a little more certainty on picking him between the 2 of you.
I could have been entirely wrong though, but it was better than going on nothing and losing the game on the night kill.
I supported a Kuro lynch publicly with Alan because I felt he might target me instead if I said otherwise, and I'd rather have had people jump on Kuro than you, in response to me "agreeing" Kuro was likely mafia.