Power is often associated with size.
Generally speaking, the bigger the hitter, the farther they can hit the ball.
But not always.
While small guys like Jose Altuve can absolutely destroy the ball, there are plenty of guys who are bigger than him who don't have his power and who can't get the ball to, much less over, the wall.
I take a deep dive into that question in Advanced Hitting Mechanics when I talk about Warning Track Power, but let me give you one word that holds the answer to that question.
While size and strength are important, they aren't worth much if your hitting mechanics are inefficient. And what is one of the first, and most important places where hitters' mechanics break down?