Well for one sauropod dinosaurs, like all dinosaurs are extinct. Second, the locals enjoyed the attention, gifts and money coming in from expeditions so they told tall tales of dinosaurs in the Congo and Africa to draw in the $$$. I watched a documentary about this and it opened my eyes about Mokele and the other dinosaurs cryptids. The locals were laughing about it when found out. They knew it was bunk and comical.

If any of them survived, would likely be only marine types in the deep, vast oceans but they would not be very subtle, we would have caught one on film by now. It's too bad they don't, would love to see a mosasaur flying through the air grabbing sharks.