I don't think this is about the specific news or Robinhood's specific actions. More likely Google have a policy (or a habit) of removing reviews that don't look "organic", or reviews that seem driven by news or agenda. App developers will more be more likely to publish on your platform if their reviews are less likely to be unfairly mobbed or something.

Just guessing, obviously, and I'm not sure how the contours of such a policy would work. Clearly organic bad reviews will often be correlated with each other, and with negative news.