If they wanted to, Nvidia could pick winners and losers in AI by withholding GPUs. That would be using their power in one market to influence another market. I haven't seen much evidence of that though.

Except as there’s a backlog if the enter into collusive agreements as a monopoly they are impacting adjacent markets (AI and adjacent companies competing with open ai and Microsoft). Also bulk pricing agreements can be seen as collusive even without inventory scarcity because it structurally advantages a picked winner.

When you hold a monopoly the same rules don’t apply. That’s why it’s often advantageous to allow material competition in your own market because your adjacency influence can be outsized and cause unintended consequences -even if you normally would have been allowed to do such things-. Those unintended consequences don’t require malicious intent they just have to exist and be materially a result of your monopoly. The more your maliciously collude though the worse the remedy will be for you.