One of the oldest games in the book, well documented, lots of people play it using CFDs or spread bets.
You haven't stumbled on anything magical, it won't be like printing money if that's what you were expecting.
Time to return to cum div is one of the things to factor into your expectations. As is the fact that if you want the dividend, you'll need to be holding before ex div.
If can be a profitable game to play, but like most things in trading, only if done correctly.