How is Google currently preventing others from "freely making their own browsers based on a standard browser engine"? In no way, as far as I can tell. They are

How is Google currently preventing others from "freely making their own browsers based on a standard browser engine"? In no way, as far as I can tell. They are paying for the vast majority of the browser engine development, and all the companies you list are free to then build high quality browsers with minimal cost and little in the way of engineering competence.