Theyre not a monopoly - thats one company holding all the cards - but you can bet theyve all colluded together to price fix and share markets along with acting as a unified voice when it comes to DNC concerns.
You don’t have to be a Monopoly to fall under Anti-Trust.
All you need is a controlling interest with no viable competitors.
This is why Intel kept AMD alive.
It kept the Gov from breaking them up.