Indeed, what happens when Elon starts his own platform instead and uses some of the ~$40 billion he'd otherwise buy Twitter with instead on paying top users of Twitter to exclusively use his platform instead?
He wouldn't bother because it'd be a failure. Twitter's tech stack isn't worth 40 billion, Musk could clone twitter for less than $500m, but just having a platform doesn't accomplish much, the overwhelming majority of twitter users have no reason to leave twitter.
For a real alternative to succeed, solid backers focused on dethroning tw are needed to inspire confidence and stability, then we all need to jump at about the same time to get the momentum going and bounce out of the twatterverse.
As it stands now, there is no real competition.
That's exactly the point - there is no reason to believe this would change if Musk created his own social network.
Most rejected the overall concept. The amt of users that stil want something similar but not Twitter AND who will be appeased by whatever alt Twitter is made is an even smaller number.
The world is littered with the expensive corpses of failed software.
Google's product lacked purpose. It died because of a lack of vision and leadership and product mistakes (real names).
It died prematurely. Google treated the product like a pilot a network threw on the first week of September. It had solid numbers and given time it could have found itself if it found a backer in leadership.