You should try reading your source…

“Experts say the American alligator’s top running speed clocks in at 11mph.”

I a fat outta shape slouch, but I think in a life or death situation I could manage 11mph for a few minutes.

Sure they can burst a good bit of speed, but that 20-30 ft sprint mostly comes from them lunging with all 4 legs and their tail as hard as they can and then maybe 1 or 2 more lunges and some scrabbling.

It’s mainly a matter of weight and gait. They got stubby little side protruding legs and they weight a ton incomparison to their leg musculature. They can high walk for a good distance, and they can gallop, but only for a few steps.