IIRC, this wasn't new regulations, it was an announcement of proposed new regulations, which was then tempered after the initial backlash with a "we're reading your comments and will take them into consideration" statement. I'm going to assume that they fired him for causing the stock plunge, unless they push through the regulations anyway, in which case it's because they needed a scapegoat.

Either way, sucks to be him. Imagine getting fired because a bunch of investors panicked when you proposed doing the only sane thing to regulate psychologists manipulating people.