Have you also consulted the actual decision-makers at the world's largest advertising corporation who sign those real engineers' paychecks?
But of course, that would require Google actually take some responsibility and do some legwork and neither of those things are in their core competency.
If Google actually had any goals of improving security, they'd literally just delete the Chrome Web Store and start over and manually reviewing and approving extensions one by one.
The results have not garnered much acclaim.
I suppose you could argue they simply haven't budgeted enough $$$$ to get skilled reviewers taking enough time on each review.
Bear in mind browser extensions completely defeat all the benefits of HTTPS. If we aren't putting them through significant scrutiny there really is no reason for anyone at Google to claim to work on security at all. Extensions need to be treated as incredibly privileged code and vetted accordingly.
I very much doubt the upper management is stupid enough to tell the grunts that they're doing this to kill off adblockers
they know there will be intense regulatory scrutiny on this at some point in the future
the true factors that went into this decision will have been discussed verbally and in-person only
It really is the case that the same mechanisms that enable adblockers ("this extension may affect your traffic on every website") are also the mechanisms that enable malware in extensions, which are not at all rare.