The problem is that the tech giants manage to tapdance around so perfectly that they stop JUST barely short of actually fulfilling the legal definition of a monopoly. It is still technically possible, albeit astronomically unlikely, to compete with them.
For an analogy, think of a crooked manager. If you work an employee for a full time week you have to give them health insurance on top of their salary, so you schedule them for 38 hours a week. That's just short of the hours where you would have to provide insurance, but still for all intents and purposes full time labor.
Same principle. These tech corporations are going riiiiight up to the point where if they got any more influential they would openly violate an anti-monopoly law, and then stopping, and thumping their chests about "wanting to give power back to the individual."