Because he's a professional narcissist, and everything narcissists do is attention-seeking and fake.
There are a number of books about Branson, and they all underline that he's "not a detail person." As in, he literally doesn't understand what he's doing a lot of the time.
He's good at surrounding himself with competent people who make things happen. He's also good at sales - talking a good game, being charming and optimistic in front of the cameras, and getting people to put up money.
But after some early successes - especially the record company and recording studios - his record of delivery is mediocre, with not a few expensive failures.
With Branson everything is a front and not as solid as it appears to be, and he has a long list of former associates, clients, and partners who are not as impressed as they were initially.
That's not ideal for a conventional business. But when you're dealing with experimental aircraft full of rich people having a very risky adventure, the potential for disaster is spectacular.
People have already died on this project, and it looks as if it's only a matter of time before it literally blows up in someone's face in an extremely expensive way.