Eagles do sometimes catch tree monkeys, swooping down and grabbing them with their powerful talons.
That’s about it for predators for monkeys in the trees. Other than ants and bugs, and the occasional snake, nothing really bothers monkeys when they’re hanging out or sleeping in the trees.
It’s where they’re safe and seek refuge from other animals that can and will eat them.
Still, they’re better off than monkeys that spend a lot of time on the ground.
All of the meat eaters from lions to hyenas seem to want rhesus pieces.