Best Ball is just a very different mindset as others have mentioned. It's purely for gamblers and my guess is mostly populated (at least among winners) by people who love big poker tourneys, game theory, etc. People are max entering the big tourneys, tracking player shares, studying builds, etc. Of course most of your teams will be trash but the idea is get a big enough portfolio and eventually it will thin away where you hopefully just have a couple teams to follow as they race towards a huge score. It's just a different mindset. If you play in a few dynasty and redraft leagues, you might think Tyreek Hill is washed up, I won't draft him or Ricky Pearsall is the man, I am taking him in literally every draft I do. Those approaches are fine in 5-10 redraft leagues but if you are entering 300 best ball drafts, you have to at some point get a baseline % of pretty much every player. Too much Pearsall could kill you and totally missing out on Tyreek could also kill you. For me, that's just not as fun as assembling 2-5 teams and making my stands on players I believe in.
Are you talking about best ball leagues, or are you solely referencing the large best ball tournaments?
Completely different things requiring different strategies.
Amongst best ball leagues there are different variations - some are just draft it and leave it, others have weekly waivers/free agency and trading.
And among the tournaments, also different variations. Some are single entry, some are multi entry. And then a ton of variations of just a full season, most points win, some are have to win out of your individual league, to advance to the next rounds,
some have teams eliminated every week, and so on.
Since you mentioned eliminator... Underdog has a wild eliminator contest with 196,608 entries.
50% of the field will be out after week 1 from the 12 teams who draft in your draft room, 6 advance. 50% cuts continue weeks 2 through 16 as randomized heads up matches 1/2 advance. Week 17 final is a 3 team showdown.
It's the ultimate sweat each week to see how many of your teams win the coin flip each week to advance and see how lucky you get with matchups. 24,576 teams surviving to week 4 are in the money. Reminds me of the FBG best ball contest we know and love except the cuts are more brutal and player selection is via draft instead of salary cap.
Comment on the gambler angle. Can't speak for others, but I just love drafting teams and trying to build bigger better stronger. When it costs 3-5 spending an hour picking players it's mostly entertainment. Watch people sniping players, scoop values, pivot when the board goes a certain way, try to push players another round, identify "my guys". I like problem solving and strategy, so it's just plain fun to me. Months later as the NFL season is getting close to FF playoffs, can check my teams. See if some drafts hit with no expectation of making any money back. Already had my fun, winning money is gravy.
I think it's best to not expect a return. Stuff happens even when you get things right. Good example: Rashee Rice was looking like a league winner last year till he got hurt. He was my most aggressive best ball take last year for anyone going in the top half of the draft. Strangely, I felt good knowing the take was correct despite the negative outcome.