Theory on Trolls, Olog-hai, and their [I]fear[/I].

[Kuruharan]

Morgoth's influence on Middle Earth was extremely strong. In fact, he put so much of himself, his evil, into the earth that lingers still after his captivity...I believe this also could apply for Trolls. Morgoth could have set their existence into motion, and even though he is no longer in direct, control over them, they still can function. It's like ripples in a pond I suppose.

Interesting, could his lingering influence continue to give Trolls life?

A better analogy might be a robot and it's maker. The robot would still continue to function according to it's programming even after the removal of the maker.

Morgoth direcly applied his will to the Trolls in their beginning, and they could then continue to function without his direct control because they, on a very internal level, knew what they had to do.

However, as has already been said, there had to be more than just this going on because the 'robot' theory is a bit too...well machine-like.