By no means am I qualified to answer this question, but my thought would be that most of the smaller fish are landed during the day when the fish are able to see best so the younger ones bite the line. The bigger older ones typically bite jigs at night (so you don’t need to be as stealth and can use heavier line) or via flying fish where the line often times isn’t even in the water. Again, just my opinion.
We spent too much time and money to get a bite and out smart fish When hungry and the right competitive mindset they as all fish will go wide. They are just on the move constantly and now know plenty of food available and just keep swimming to the next unmolested bait ball to destroy. Nova Scotia footage fish up to a grand you would think to be smartest survivors roll through Herring nets and eat baits 3 feet from the boat with dam near rope as a leader .
I think the big ones are deeper and usually caught more in the dark. The massive schools of smaller ones more in daylight chasing bait balls and stronger competition in good light.
Just an observation.
A lot of times when the big ones are around they are just as line shy as the smaller ones. The reason they get caught on bigger line is because the captain tells everyone to use their 80lb and 100lb outfits when they see the bigger fish on the meter. They catch a few on the bigger line but they definitely bite better on the lighter line.
I have been on 2 trips this year where the bigger ones didn't want to bite. On one trip I fished all day without a bite and finally grabbed my MXL raptor with 40lb out of frustration. I threw out a nice bait and got bit immediately and then I got spooled just as quickly. On another trip I wasn't getting bit on the 60lb and 80lb line and then the skipper said that this school was smaller fish and you could use lighter line. I threw out my 30lb and got bit instantly by a 100lb to 125lb fish. I fought it for 2 hours before I lost it right at the boat. Occasionally you will find a school of big fish that will bite the heavy line but that is the exception and not the rule.