>>615420301. Bettel is flat out a better streamer than LCC was. His humor and timing have been refined. He's not fundamentally different, just more confident in his act.
2. Visibility is a big deal. There are plenty of big creators that have been doing the same thing for years but only got and stayed big because someone bigger plugged them or they by chance went viral or whatever. There are other god tier entertainers out there that will never escape 2 view status because no one will see them.
3. They might not be appearing in front of the right people. Bettel shared a lot of similarities with Jerma for example, but he might not be known to Jerma fans, and the ones that do know him might not like vtubers. Reminder that he had a sizable following even before he was LCC, and you saw a bunch of comments going "ew, he's a cringe vtuber now" when he became LCC despite his content not really being different.
In general, there's a lot of factors why someone might not get big despite having all the ingredients of someone that should be big.