So look at tiny men like Sokaku, Sugino and Kyoichi Murai and wonder how they could completely dominate much larger and already-well-trained men of considerably greater weight.
Staying out of the argument overall, I would point out that saying this sort of thing does little to forward one's position. The retort would be "well, then, imagine how much *more* powerful they would have been had they been bigger!"
I have some sympathy for those trying to throw me at times. I'm about 240 pounds. 6 feet tall. Barrel chested Norwegian stock with no legs and all upper body. So a low center of gravity, lots of muscle, very dense (in many ways), but also with extra weight I would certain rather not have (another discussion). It is very hard to move me. And when i do certain throws where I'm dropping someone down... Well, me dropping my weight down into my hands vs. someone who weighs half of what I do dropping their weight down into their hands... Big difference.
The issue is however very complex which is why these discussions tend to go nowhere. We try to speak in generalities while simply picking and choosing those things that benefit our point of view. Confirmation bias. So what I wrote above as a response to some comments I think is perfectly valid point -- extra weight is great on anything you're doing that involved "weight underside". And then transmission of that weight into the attacker. I'm sorry, you can't make physics go away. Of course that same person may not be as mobile, as healthy, as fast, or whatever due to that extra weight which creates disadvantages as well.
In other words... The question is flawed because it is too general. And most are correct within their narrowly defined scenarios.