The same group has a reputation to uphold (i.e., that of 'honourable' criminals), so they just move on to the next target, who will, incidentally, know that they are absolutely true to their word. (This is why paying off ransomware hackers is being made illegal in a number of countries.)

A different group? Certainly. I wouldn't want to be in the shoes of the infosec guys at Canvas right now.

Simple economic motivations from the hackers. They've hacked a lot of different companies. [1] If they didn't keep their word then companies would have no incentive to pay, and vice versa when they do keep their word.

[1] - https://en.wikipedia.org/wiki/ShinyHunters

It might make more sense for Shinyhunters to request a reoccuring charge to smooth out their revenue stream. Basically protection money as it was called in the good old days.

This is of course assuming that Instructure continues to be relevant, and that students still believe that college education holds economic or social value.