I highly, highly doubt that the share of people who consistently stay in category 1 year-over-year is more than a couple percentage points. Lots of people put $50 in to try the whole thing out, lose, then never return. Extremely few people will then return in 2025 and be like "lets do that again".
I cannot for the life of me understand why these apps can't make money off the pros, and instead need to ban them. Ignoring all the dumb promotions these apps do: Sports betting is zero sum, you're betting against the other players, not the house. The odds are set by who you're betting against. Literally, how does it not work out that the profit is just the money from the losers minus the house 30%-or-whatever cut? Is "pros" in this context people who also frequently abuse the (oftentimes wild) promotions these apps run?
But, if it did work like that, the problem is even more apparent: these apps are at best a direct wealth transfer from addicts and idiots to corporations and pros. Wait, I just described the stock market, we're talking about sports betting :)
In sports betting you are betting against the house. If the sportsbook sets a bad line, you can lock it in and make money off of it.
Horse racing is what you describe, parimutuel, where the house just takes a commission. But the odds shift even after you place your bet. Very different for traditional sports betting.
Sports betting is zero sum, but the market is very inefficient. So you need market makers (the gambling sites) that will fill any order and that set the initial price.
The correct price is often not known for a short while, and that's when the pros bet. Immediately when the line (price) comes out, if they think the line is miss-priced, they will place large bets.
Eventually the house realizes the mispricing and they change the line, but by that point a pro might have placed a six figure bet.
So pros really are winning from the gambling sites, not from other gamblers.