Re: "I had this idea that life would adapt to the deep"

Falling nutrients are *not* necessarily gobbled up by things higher up. What happens to a whale carcass falling to the ocean floor is a great example of that. Sure the whale carcass is going to fall through a whole lot more water to get to the bottom of the Challenger Deep, but most of the noshing action happens when the carcass has hit the ground, not as it descends. And the "sludge" kicked up by the submersibles will be pure nutrients - dead stuff drifting down from above.

The heat is the more pressing problem (even more so than the pressure itself). Life probably can make itself at home there, but only under conditions (becoming relatively large and moving veeerrrryyyy ssssllllooowwwwlllly) which minimise energy expenditure. So complex life, and in particular predatory life, are not likely to be happening.