Many people loved "Old School Toribash" in the 2006 era, where a ton of the players who are now Torilegends and in legendary clans came from for the most part, and those first three clan leagues were all single mod matches. From that time, until somewhere in the neighborhood of 2013, Clans existed far far more as a social gathering of people who interacted a ton in their own rooms, playing the mods they enjoyed most, along with a few forum/staff orientated clans. Clan League was the end all be all, but nobody touched their rosters in the interest of winning it per-say. Even Alpha, which developed a reputation by around 2014 to be the "do whatever it takes try-hard clan", still for the most part only invited a few rare people who had to be exceptional at Wushu, since that was their niche. RAWR won the last clan league in that super pure, "here's our members lets do it" style.

The turning point, from my perspective, was TGS winning Clan League. There was quite a bit of hostility, because it felt like the first year that there was "E-Sports" brought to Toribash. Many of TGS players were duelists, some of which getting banned repeatedly for scamming. It was sort of unheard of before then that a "top tier competitive clan" would hold onto any clan mates that'd be disrespectful or get banned. If you were getting banned, especially stuff like duel scammed, prior to this era, you were probably kicked from the clans like RelaxAll, Urban, RAWR, Alpha, etc. etc. and it honestly almost never happened anyways. So when an unofficial clan came in with alts, duelists, memes, and whatnot, Alpha got super defensive about the whole ordeal. While obviously TGS had a much different perspective, that they were just all legitimately great friends and weren't simply duelists coming together to win Clan League, Alpha went onto the recruiting hunger, neglecting inviting people who were the absolute closest friends and great wushu players, and instead sureing up weaknesses by inviting people who were good at clan league mods. That manifested in Alpha winning in Clan League 2014 with that strategy. On a personal note, this is the main reason why anyone even associates my name with Judofrac (okay so mostly people think of me as an obnoxious POS staff member, rager, and overall immature lunatic but) when Alpha was going try-hard, it become glaringly obvious that I wasn't the best wushu player in the clan, and that was the only mod I played for like... 5 years. So to become a threat for Clan League, and to be useful to Alpha, I played a shit ton of Judofrac. I fell in love with the mod way later after tons of matches but me even playing that mod has everything to do with making less weaknesses for clans in Clan League.

Now, moving forward, from 2014 onward, the playerbase got smaller, meaning monopolizing the talent of people who are actually good at this game that much easier. So Alpha wins 2014, RelaxAll invites FistofLife, a player they'd never in a million years invite prior to the changes in the competitive climate, and win 2015, Parrot consumed most of Alpha after a lot of internal disputes, as well as some other free-agents like Cold from Ultimate dying and the talent that already existed to win 2016, and Alpha regained the roster lost and took on additional carries from Parrot's last year roster, plus cowmeat and mwah if they so chose, to make clan league 2017 seem pretty over.

If there's less and less players, it becomes really really easy to monopolize talent. The ONLY reason it's not a "sure thing" is because a) Toribash has a ton of luck and b) 8 games isn't so much that the "depth chart" of your clan isn't insanely relevant. Essentially, 2 good players make up a clan that can handle the entire winning of clan league. Thank god though, because if they limited how many games an individual player could player further, clans that monopolize talent would be impossible to take on.

tl;dr: Clans used to be super loyal and none existed JUST to win CL, Clans started recruiting and monopolizing on that basis, top players now congregate to the same 2-3 clans because they have no chance winning otherwise, player pool is small, Clan League is now tryhard as shit.