FB stock hit a low at ~$157 right before Zuckerberg's April 10, 2018 testimony to Congress, and bounced back into a steady increase, hitting a then-all-time high in late July before going into a dive after the earnings report. The July 2018 dive was attributed to missing revenue expectations, but AFAIK, the general opinion [0] was that when it came to public fallout specifically related to Cambridge Analytica, FB weathered it quite well – hence the stock's steady climb from Zuckerberg's testimony until the July earnings report.
That confidence in the stock is obviously not just from good PR, but I don't see the evidence that the PR folks fucked things up either, given how much potential damage the CA scandal was predicted to cause.