Every accusation from Trump is some random line he pulled out of his ass on the spot, and people like you keep falling for it and trying to divine some grand strategy out of it.
It's not random.
There are exceptions -- birtherism comes to mind -- but that's what they are, exceptions. In general, though, accusations from Republicans reliably reflect things they are either already doing, planning to do, or wish they could get away with.
He can just have wanted to punish Iran or something without it being a full blown plan. Trump assassinated an Iranian general during his first term [1].