I also don't understand quite why there's disagreement here, so perhaps it's best to just end it here. From my perspective what the oversight board says is simple: Trump was banned, but not because he broke any actual rule, as evidenced by the fact that everyone else on the platform can do the same things and not be banned.

Perhaps you're interpreting it differently as: he broke a rule, which happens to only be enforced against people named Donald Trump. Well, most people wouldn't recognize such things as genuine rules, which is probably why the oversight board had such difficulty with it.