nothing Trump says really has any meaning.

This is reductive. Why report on anything he says then? But for the sake of argument let’s go with that.

When he says something happened “in the past”, it could mean it happened at literally any time previously, it could mean he expects it to happen soon and as such is an inevitability so he just says it already happened

So how do you go from that to concluding:

othing from that “context” makes me any less likely to believe he found out what Nvidia was minutes before taking the stage

You’re not making any sense. You’re saying “you can’t trust a word that comes out of Trump’s mouth” and refuting his whole quote, while somehow holding up the conclusion that he didn’t know anything about Nvidia before walking on stage with, per your own standards you just emphasized, zero evidence, out of thin air.