This is dementia.

What happens is that pathways in your brain start to break down, so when you're trying to form a connection, the connection just isn't there. But what your brain does is it tries to be "helpful" by routing around the damaged pathway without even telling you that it's doing this.

So part way through trying to talk about bond markets, something he doesn't really have a deep pool of knowledge on to begin with, Trump's brain ran into a block. To fix the issue, it took the last word - intervention - and formed a pathway from there. This lead to "military", kind of like an LLM losing context but continuing its next word guessing.

He probably finished out the sentence without even realizing that it has zero connection to the original question he was supposed to be answering.