The meteor didn't kill most of them.

Some were killed by the tsunamis it produced. Or shockwaves. But I don't think many were killed by the meteor itself.

Most were killed by the sand that kicked up in the atmosphere all over the world, then fell back down as a rain of glass.

The rest either succumbed to strict competition when the sky went dark and starved, or evolved into chickens.

Seriously guys, spend an afternoon with a backyard farmer and just watch their chickens. They are little cute dinosaurs. Watch them run together, or hunt in packs. Watch their little talons stretch out as they step...clearly Spieldberg's inspiration for the T-Rex footprint scene. Hell, if I'm a little late with breakfast, they'll surround me and start pecking at me! Like I'm the food!