Size and strength are definitely pretty big factors in fighting but when there is a large discrepancy in skill it often negates even a substantial difference in size.
Just remember the first few UFCs where the smallest guy in the tournament, Royce Gracie, pretty much ran through everybody despite being outweighed by as much as 50lbs due to his superior skill and ability.
Sometimes, though, the difference in size can be too much and regardless if the smaller man is way more skilled, the bigger guy's physical advantages are simply too much.
In this video, we see an example of pure size and strength not only overcoming but completely dominating a much smaller man even though the smaller man is a wrestler and the bigger man apparently just a weightlifter (powerlifter to be exact).
We can see in the video below, the difference in size is really significant and it looks more like a man wrestling against a boy who is unable to really get anything going.
This exchange here in this video is almost reminiscent of the classic Pride FC fight between legend Antônio Rodrigo Nogueira and Bob Sapp where the size and strength of Sapp posed a lot of problems for Nogueira who's elite level grappling was nullified early on. However, in that fight, once the legendary Nogueira got his bearings, he was able to defeat Sapp despite the huge difference in size and strength.
The size difference in that one wasn't nearly as significant as it is in this one, however, as Nogueira himself was a pretty big dude (around 230lbs) while the wrestler in this video looks to be more like 130lbs.
While the small wrestler pretty much gets manhandled here, around the 1:20 mark of the video he has some success and pulls off a nice throw on his absolutely gigantic opponent which is very impressive.