Agreed, none of them are imitators. Proteges, yes.
Zawinul got his start with Cannonball Alderly, and one of his early compositions (Mercy Mercy Mercy) has big fusion vibes to it.
Hancock is just a Miles level genius. My piano teacher told me something like "I can play at Herbie's standard for a 5 minute stretch, but watching him keep at it for 90 minutes solid ..."
McLachlin is a hippie who cut his teeth on the late 60s modal/fusion scene.
In a Silent Way is my favourite jazz album ever. I think the history was they did Bitches Brew, then after that straightened that approach out a bit to make something more accessible.