However, AFAIK Bethard is not publicly traded, so Ibra might be guilty for this if he knows that the parent company bought the stocks.
It is pretty clear really. If he owned it as part of a mutual fund (and the company was large enough to be included) then any possible benefit he could derive from that ownership would be heavily diluted. However when you own a large chunk of a betting company and are an active athlete then all sorts of corruption can start to seep in. The rule is there to stop abuse, he could cause all kinds of mayhem on the pitch and rig results of games in many different ways. Someone at his age and level of the game should know full well that this would not be acceptable for those reasons, so it looks like he has gone out of his way to be deceptive. It's a shame that fines are not proportionate to someones salary, because the 100k limit (even for a "first time offender") is absolute peanuts to these players, they've probably spent that much on a great night out before - if they lost 10% of their annual salary instead it might discourage such behavior in future.