It's not like people actually take the time to determine exactly how many stars is considered fair. I believe that if this rating system were replaced with a binary vote, like thumbs up/thumbs down, Google would've still removed the thousands of votes.
I understand the argument for removal, since Robinhood likely had no choice but to stop the trading. Ratings are meant to inform consumer choice, so a brigade of downvotes due to some recent controversy/memery is more likely to hurt consumer choice since it reduces the amount of information available. It means that one detail is drowning out all of the others, and regardless of whether a new customer would care about that detail, the fact is that it's the only one they'll be able to base their decision on while those votes stay up.
But on the other hand, app ratings are one of the very few powers consumers have to affect change in companies they do business with. Brigading the rating system (which has the effect of turning away new customers) is no different than bad word-of-mouth, where angry customers go out of their way to prevent others from doing business with the company that screwed them over. Even if a disgruntled customer goes a bit too far with hyperbole, that's their right. And it's a good thing that those things are possible, because it forces companies to always stay on their toes and think twice before doing something to hurt consumers.
It's the question of whether a consumer should have to "suck it up" when a company screws them over, or whether a company, whose full-time job it is to provide a particular service, should be held to a higher standard and be hurt when they provide bad service.
IMO, Google really should have not gotten involved here. This is an issue between Robinhood and its customers, whether or not you think what Robinhood did was fair. Google, a company being investigated for anti-competitive practices, just took another anti-consumer action.