Could also be that SpaceX cracked it then other companies began poaching the engineers and the other companies started getting tips on how to address the hardest problems.

Investors. Investors finally realised that it could be done.

I'm sure engineers and science-fiction writers have known for a long time that it could be done.

Even "Musk realized it could be done". He had a few good ideas. Or pushed for a few good ideas until they were put in practice.

Unfortunately then he stopped taking his dried frog pills and look where he is now...

Did Musk realize it could be done, or did he pay some engineers to realise it could be done?

... pay and convince people to give him money to pay ...

I still think he had some merit in the past.

Musk from the beginning realize to reduce the price, he would have to solve re-usabilitly. So he and the company from the beginning was focused on re-usability. He didn't just say 'this is what we are gone do'. As the company grew and solved initial problems of launch, they slowly figured out the best way to do it. And Musk as CEO was deeply involved from the beginning and and involved in all decisions.

When companies fail, is it the result of leadership or employees? Companies need great employees and leaders to succeed and without both, they typically fail. Hiring excellent people then motivating them all in the same direction is very difficult. Being such a leader and having access to capital and being willing to risk bankruptcy in very high risk endeavours like this is exceedingly rare.