There's a lot more to the Truth Social story, specifically as it relates to the reason the app was established. If you are Trump, you're potentially looking at a promise of no further bans on Twitter vs. a certainty of no bans Truth Social along with a broadcast platform you own.
Its not a clear cut thing that even if Musk buys Twitter -- and even if Trump is restored to full posting rights + all posts restored + all followers restored + no restrictions, etc. -- that Trump wouldn't still finish the development of Truth Social and have it operate as a direct competitor.
Actually if I were Trump I would finish the development of Truth Social, go on Twitter and as part of the broadcast output messaging tell all my followers on there to join Truth Social, in addition to whatever societal / political messages I wanted to push out.