Straightforwardly, nobody with the resources to build and maintain a browser could ever be trusted to do so, as they get those resources from somewhere, and it's going to be somewhere unacceptable (ads, trackers, Google, taxes, selling the browser or addons/features as a product, hostile nation states).

These things are far too complex and expensive to be produced as they should and as most FOSS is: for free, by a group of individuals who could fit around a breakfast table and don't answer to anyone but each other.