Re: Yep, there's a huge difference between ''wiped out" and "nearly wiped out".
Moa, Ostrich, Rhea, Elephant Bird, Penguins, ...
I don't see many of those 'hopping around in the treetops'.
I suspect the flightless birds evolved from flying birds, rather than being dinosaurs that couldn't climb trees. Even though they're grounded, they retain most of their bird-like adaptations, such as wings and beaks. That's why they're "flightless birds", rather than "feathered dinosaurs".