Do short boxers get their power from their legs?

[pesticid]

Manny Pacquiao
Mike Tyson
Keith Thurman
Lucas Mathysse
Marcos Maidana
Naseem Hamed

On the other hand you have Bradley and Berto who have chicken legs and they don't hit that hard. I think James Kirkland is the only exception that I can think of as far as having skinny legs for a short guy and hitting with tremendous power. Do you have any more example for or against this theory?