It's still impossible to prove the files were deleted even if they don't release after the initial payment. All it takes is a single individual in a group to make a backup or have a default policy of keeping a backup "just in case".
One should assume at this point that it's not a question of whether the files will be leaked but when.
also, governments like china, North Korea , Russia, Iran are basically silent endpoints for this stuff, so assuming it's valuable data, the ransom request should trigger whatever intelligence protocols you have.
Obviously. The surface for such an enterprise is tiny, while a worldwide multinational with hundred of thousands of employees and contractors can't afford that luxury.
If they were the tiniest bit decent they wouldn't be working in ransom ware.
If they delete the files, it's not out of decency. It's out of a desire to build a reputation of post-ransom trustworthiness so others will pay in the future.
Low Earth Orbit. It has become sentient as more starlink satellites have gone into orbit. As starlink is used to transfer data LEO has become interested in the uses of the data transfer. Being of Lawful orientation LEO doesn't like ransomware, and may at some point use its computational and communication abilities to redirect any ballistic missiles or rockets which are fired into LEO at the points of origin of the ransomware demands.
If one group got it, there's no reason to assume another group didn't also get to it first and simply sat on the data. There's also no reason to assume the group holding your data ransom is acting as a single reasonable entity: it could be a group of people, each with a copy, who all have different opinions on what to do.
Sometimes the groups want a good reputation for not disclosing stuff if the ransom was paid. They earn that reputation over time.