They've always been at war with ad blockers. It's just most major multinationals have matured or diversified to a point where they are functional monopolies, and no longer gain any value in competition or service improvement.

At this stage of the merger and consolidation phase of global capitalism, with captured governments that won't dare break them up or fine them more than a meek virtue signal, the most cost effective way to satiate the infinite growth of capitalism is to increase the exploitation and value extraction of their existing user base as much as possible (aka enshittification).