I'm not going to defend the overall conspiracy here but I totally buy into the theory that Google would prefer a big brand ranking over several small businesses...

The logic in my mind is -- Google wants the rankings to be unequivocally trustworthy, e.g., if I'm searching for an espresso machine, would I trust a small ecommerce shop where the experience could be terrible or do we just throw an Amazon or Bed Bath and Beyond result at the top because those are vetted companies.

Sure, the little guy has to grind to get a better ranking and free traffic, but it should in the long term encourage better behavior by companies as they attempt to earn that trust.