That isn’t quite right. If you stopped paying the bank would kick you out and sell the apartment to someone else, but if they get less than you owe them for it, they will also send you a bill for the remainder.

And then sue you to get that money.

Interestingly, if they get more than you owe them for it, they will cut you a check for the difference.

But you are actually wrong about how and what the order of operations is.

You are buying the house, the lender (bank) writes the check directly to the seller, and you sign a mortgage agreement for that much with the bank and they put a lien on your house. The bank does not own the house, you do. The bank owns a promissory note from you, backed by your personal wealth and credit and the value of the house (that they have a lien on).

In the case of Twitter, yes, Twitter itself is part of the collateral, but so was Elon musks personal wealth and Tesla shares.