Here's the "Oscars love curse" in a nutshell:
It basically just means that after someone wins an Oscar, typically for "Best Actress" (but still possible amongst "Best Actor" winners as well) their significant other will cheat on them soon after, resulting in a breakup or divorce.
Although, we can't say for sure why these couples broke up, for the sake of this argument, let's say it was due to being cheated on. It's a common enough reason.
If you're not superstitious and think that this is all a coincidence, then sit back, and allow me to show you all the evidence proving otherwise.