So what did Trump say/do to make these 4 people decide to kidnap and torture a mentally challenged person?
'Make' isn't the right word. Probably the opposite is true.
But he did run a campaign that exploited a lot of hate and anger.
Which empowered a lot of angry, hateful people.
And their anger and hate is drawing a reaction from people who feel targeted by the anger and hate.
And, big surprise, it's gotten out of any one person's control.
So, no, Trump didn't make (force, coerce, direct, order, whatever) this happen. but he did create the conditions in which it happened.