Smart and Dumb Explanations
If the Trump administration were smart, here is how that move would make sense. Trump's people were smart enough not to email about their collusion with the Russians. But they did talk about it on the phone. Trump's allegation serves the following purposes:
1. It tests whether the Obama FBI actually was listening in while Trump's campaign staff discussed their collusion with Russia. A strong, immediate denial is a sign that the Trump campaign has pulled it off and people won't be indicted. A non-denial denial means they have to keep worrying.
2. Regardless of whether the FBI was listening, it might lock the FBI in to one version of events or the other. If the FBI denies that it was listening, then it will look ridiculous if it later tries to introduce evidence that it obtained from a wiretap. On the other hand, if the FBI admits that it was wiretapping Trump's campaign, then it can be cited to support his ridiculous claims about the legitimacy of the popular vote etc. The point is to force the FBI to commit to one or another. Whichever way it goes, there are advantages for Trump.
Remember, I'm just pointing out how the move would make sense if the Trump people were smart. I'm not saying they are smart. For instance, here is an explanation assuming they are as stupid as they seem:
1. Trump knows that his campaign colluded with the Russians, but he thinks they were smart enough not to get caught.
2. But the Democrats and the media are pushing the question as if they know they will find something. (This is debatable, I'm just saying this might be how it appears to Trump.) It's like in The Wire, when the cops know exactly which car to pull over or which house to raid—something isn't right, the cops don't just get that lucky on accident.
3. Therefore the Democrats must have some unexpected source of intelligence. Trump's mind immediately leaps to a wire, and he impulsively tweets it out. "I've got you!" he thinks to himself. "You would never know this shit if you hadn't tapped my phones!" He is in full-on Avon Barksdale mode, if Barksdale were a moron.