Sometimes it's also just a genetic gift.
I remember a story that Bill Wallace told about sparring with Joe Lewis where Wallace said he hit Lewis with the best kick he has ever hit anyone with, ever, and the only reaction he got from Joe was, "Ow."
I've seen Shihan Charlie just grab a hold of people and have them tap out, or just toss people through the air like a "hammer throw," or just collapse people's legs straight down into the ground from a standing clinch. Locking up with him feels like wrestling with a marble statue, no budging him in any direction, that is until he flings you through the air and you suddenly feel like you are wrestling with a Bull. And again, I've him do this to top level grapplers, so it's not just me.
I wish I could tell you that anyone can reach that point, but I've met multiple World Champions, top level Combat Athletes, top level coaches, many of which have devoted their entire lives to training and are top of the food chain in terms of their skill, knowledge, and experience. But I've only ever met a couple people who fit this genetic freak juggernaut type of model.