Other responses have this pretty much covered, I’d just like to add the reasoning (or my thoughts on it)
Google is trying to provide the best experience it can for users, not advertisers.
Although they technically make the money from us, if the people making the searches had a poor experience/had a better experience somewhere else and abandoned Google shopping, us advertisers would not be far behind.
Because of this, Google has spent insane sums of money to build AI which understands the context of a users search. That AI understands that when somebody searches for a brand, the best results to show are a) The brand the user searched for b) other options which the user may not know about, but could meet their requirements.
Isn’t that what you’d want if you were shopping?