If Punching power comes from the legs

why is it the power of an old puncher doesn't leave him despite him being less mobile and not as fast or strong on his feet? what you get everytime someone posts a pic of pacquiao's, tyson's calfs etc Tyson doesn't have huge calfs, he has huge thighs.

Because when they're using their punching power they're not mobile. They sit down on their punches when they throw.

It doesnt come from the legs its starts at the legs and unwinds like a corkscrew , strength stays pretty much into the 50s but speed and recovery declines from 30 year old onwards .