Why the aggressive tone?

You are right. I am conjecturing about Trump's motivations.

On Musk's motivations, he has said outright what he thinks about this. He predicts that in not too long, AI will take ALL jobs, and everyone except the rich will have to be on universal welfare. Google it - there are recent interviews of him saying that.

On the AI elements, it is much less conjecture - the trends are pretty clear.