it's a huge deal for google. they control the browser used by the vast majority of users, and the engine behind the one (such as edge, opera, vivaldi, etc) used by still more. they rely on those users to see and interact with ads to make money.
besides the obvious--driving traffic to their web properties that have their ads; they get to siphon off all that sweet user data which makes their ads 'more valuable', and control addon functionality and restrictions as well as the primary 'marketplace' where those addons come from. their ultimate goal of killing off ad blockers completely, the limits mv3 puts on adblockers is just the next step in that direction.
should a third-party acquire control over chrome's development, mv3 gets shredded. restrictions and limitations on adblockers get scaled-back or reverted outright.