Metasoccer's market cap is a little over 400K, in other words, very few participants are in this market right now.
Meanwhile, fantasy sports is a 24B+ market, with football (aka soccer) being the world's most popular sport, and fantasy football (soccer) a craze in many parts of the world.
The argument to get in on MSU is a rather easy and clear one. Buying into a microcap like this, you're basically trading awareness: buying something known to be big, but of which a lot of people are still unaware of. Here's a thought experiment for you: Taylor Swift is probably the most popular singer in the entire world. Imagine you and a few other people knew one secret no one else knew: she's coming to your country and there are only 100 tickets for the show, each at $1. Wouldn't you want to buy a bunch of tickets to sell later (if that's legal in our country ;D ), even if you're not a Taylor Swift fan or even if no one else is talking about the show (obviously, as it is a secret)? Of course! Because you'd be profiting off information asymmetry - something you know others don't know - yet ;) It's thus very reasonable to expect a somewhat analogous situation with MSU: we know football/soccer fantasy is huge and that Metasoccer is a rather good game but mostly unknown (400K market cap, remeber?).
It's a bet with a huge upside potential, one I've been in since the beginning.