Why do some people find hurting others or committing cruel acts pleasurable?

They look to provoke an emotional reaction from you and obtain fuel. It is always about the fuel.

Tears, frustration, anger and hatred are all delicious emotions which will fuel them and they provide such a magnificent and stark contrast to all of the positive fuel that you can gaze that the effect for them is considerably edifying and invigorating.

True sadists don’t provide support.They are too concerned with themselves and their daily hunt for the fuel that they need to be concerned about you.They are engrossed in their own world and have no interest in yours. The only time they pay attention to you is when you are providing them with fuel or you stop providing them with fuel. Everything they do is focussed around themselves. This is because they have to obtain fuel, as without they will disintegrate. The hunger for this fuel is never ending and accordingly all of their energy must be applied towards obtaining it. This leaves the with nothing left over for anyone else.