Extensions prior to MV3 were notoriously insecure and granted extension developers a very wide attack surface. Assuming that Google only has a sinister reason to switch to a better standard in an ecosystem riddled with ill-intentioned actors is a bit too cynical.

> very wide attack surface.

Do you have details of specific realistic attacks that were possible under MV2 and now impossible under MV3?

No, it's not. They could easily have solved the problems without introducing changes to cripple ad blockers, but they decided their investors need some more cash. Actions speak.

Google will only ever push major updates that are neutral or beneficial to their ad revenue. I do not believe they killed MV3 due to ad blockers, but it's the type of proposal that can survive at Google.