Sport arbitrage is something which is very difficult to do and you cannot do it alone. First you need at least 50 different sportsbook and look for a game where the odds maybe at one game is 2.10 and at another sportsbook is X2 doublechance 2.05 and up, if you find this, you are sure to be in profit as both odds are over 2, as I said before this is extremely difficult to achieve and you need a team studying odds all day for this and having access to as much sportsbook as you can.
It becomes popular because Bitcoin is also getting more used and that is why I think.