Monkeys like bananas because bananas are sweet. In the wild, most monkeys have a diet that is mainly comprised of fruits. They are thus naturally predisposed to like fruits. Bananas are a particularly sweet fruit and they are thus a delicacy to the primates.
Trippy Monkey with a Banana is a remix of Oleksandr Pidvalnyi photography called Brown Monkey https://www.pexels.com/photo/brown-monkey-321552/
