This is mainly about web platform standards. When google controls the only remaining browser engine, it effectively controls web standards (or in other words,

This is mainly about web platform standards. When google controls the only remaining browser engine, it effectively controls web standards (or in other words, independent standard documents lose meaning since Blink is the standard). Google is then free to push the web technologies in the direction which benefits mainly Google (think AMP) and which further tightens their grip on the web.