I think it's clear that he's simply too old to understand what's going on. By his own account, when he talked with Trudeau yesterday, he was confused why Trudeau couldn't tell him when the next Canadian election was and concluded that he must be planning to "run again for Prime Minister". Because Trump has a reputation for dishonesty, people tend to assume he's lying when he says nonsensical things, but as you say it's hard to imagine what strategic value there could be to lying about this.