Twitter is a global social network. Clearly Musk made some very questionable business decisions e.g. changing the name, the aborted attempt to ban links to outside profiles, etc, but that period seems to have settled, and the main reason for leaving now is the rightward politicization.

If you live in the US then yes that's a seriously compelling reason to leave, but a large number of Twitter's users are not using English, they're not involved in US politics, and don't have much reason to switch unless Musk seriously upsets the operation of the platform.