The distinction between "having a lien" and "owning the company" is a false dichotomy. "Owning the company" and "controlling the company" are different, though.
It's 100% not. It's secured debt, that's it. If Twitter becomes worth $17 billion, they get - $15 billion. If Twitter becomes worth $170 billion, they get - $15 billion.
To say nothing of if Musk misses a payment, are they really going to foreclose? Or would they renegotiate?
That's not an option. They all have to sell their shares. It was a corporate decision.
In fact their was another vote that meant Musk couldn't accumulate more than 15% on the open market.