> misissuance of GOOGLE.COM or FACEBOOK.COM would be detected and unlikely to be successful
Eventually detection is almost certain, but whether it's "successful" would depend very much on what somebody was doing with it and why.
We have some examples to work with in analysing this, where certificates for Facebook or Google names were issued at various times without Facebook or Google knowing about it - and maybe I'll do that analysis later, but for now I want to focus on your Hollywood Action Thriller scenario.
Google did not "kill" the "largest best-known CA in the market".
Back in January 2017 Andrew Ayer wrote to m.d.s.policy about some certificates Symantec had issued for names like example.com (sic) which Andrew had verified were not asked for by example.com's legitimate owners. This gradually spiralled, with Mozilla producing a fairly substantial document listing well over a dozen distinct problems, both newly discovered and dating back a little way, with Symantec. Overall the impression we got was that Symantec management were not delivering the oversight role needed to ensure their CA achieved what a relying party should expect.
Symantec management didn't like where this was going and tried to "go over our heads". I have no idea whether this worked for Microsoft and Apple, and for me there isn't anyone "over my head", but at Google it appears to have made things worse.
In summer 2017 Google's plan asked Symantec to replace their infrastructure and institute bottom-up change to their organisation in order to restore our confidence in the CA. For practical reasons (it's hard to stall your customers for perhaps 1-2 years while you fix things) Symantec would have needed to continue selling certificates during the period when we did not trust their management to operate a CA, and so they'd need to find another large CA to provide us with the assurances we need while retaining Symantec (or Thawte, Verisign, etcetera, all brands of Symantec) branding.
Symantec negotiated with DigiCert to provide this capability over summer 2017 (very small Certificate Authorities would not have been able to practically do what was needed) but at some point during that negotiation they pivoted to instead selling the business to DigiCert.
Once the initial agreement existed in October 2017, DigiCert and Symantec sought permission to go ahead, and received it on some simple conditions (Mozilla's concern was that this might be something akin to a "reverse take over" in which Symantec would dodge the intended management changes and instead seize a new brand, key people at DigiCert were able to assure us that this was not going to happen), then all the usual business stuff happened, and in parallel DigiCert began building a new issuance infrastructure for the ex-Symantec brands, more or less as they would have under the original concept but with them keeping the profits.
In practical terms Symantec chose to exit the CA business a bit less than a year after Andrew's original post to m.d.s.policy, after many months of discussion across about all the issues raised.
Now, if you want you can speculate about how _hard_ it is for incompetent and untrustworthy people to become competent and trustworthy, but Symantec decided they weren't interested in that path so we'll never know. Nobody killed them, they decided they weren't interested in reform.