It's all luck, really. Bad Parenting is also free on Itch.io and only takes about 20 minutes to complete — yet it made over $100,000 in sales on Steam.
Personally, with Dead Tapes: Fading Father, we made $400. The refund rate was 16%.
You don't have to release your game on Itch.io — you could go straight to Steam. But then there's a real chance no one will even hear about your game.
For example, Bad Parenting probably wouldn't have become popular at all if it hadn't been released for free on Itch.io first.
If you release it only on Steam, you might earn more money per copy — but there's also a chance your game will be completely overlooked.