The chances are very good that they did hide out in trees a lot prior to about 65M years ago. Then, after things warmed up a good deal from the after effects of the Yucatan impact and its nuclear winter, those that survived found it a lot safer than it had been to walk about in daylight. The difference was that a lot of the prior hierarchy of food-chain entities were gone, including the big meat-eater dinosaurs. So the current theory goes, anyway.

It is fairly certain that we have, at least, a common ancestor with chimpanzees and bonobos.

And they spend a lot of time messing about in trees.

A