I mean, remasters fall into 3 categories.
1 is fan service. Fans love something that's become harder to access, so remaster.
2 is a proof of technology. Creating an entirely new game from scratch is difficult and time consuming. Remastering something onto new technology is somewhat easier and quicker. It can be a good way to test something out, get your staff up to speed, and learn. It's also true when the tech side of a project becomes ready sooner than the content side can move, so rather than have idle staff, you put them into doing a remaster (super rare, but happens)
3 cash grab
Most are probably something of all of the above, or at least, they're hopeful for #1 but doing it for #2 and #3. For Crytek, if they're doing this internally, it's definitely #3 and part of the others. They have done major layoffs, so they don't have as many people to ideate. They also need cash badly. And they hope people are craving more Crysis.