Donald Trump is only president because James Comey broke every norm and tradition when he released that latter the week before the election. That was enough to tip a few more Republican leaning votes in the Blue Wall of the Rust Belt and throw the election to Trumpelthinskin. A lot has been written about how Trump has to dominate and win every encounter. He is the living embodiment of the Ricky Bobby Principle. This is why he was pissed that
There is another aspect of Trump that applies more broadly to the GOP, but can apply to all of us, I guess, and that's projection. If you are especially lacking in empathy, you are unable to see things from another person's perspectives. Lack of empathy is the defining characteristic of today's Republican party. Therefore, when you look at other people's actions, you can really only ascribe your own motivations. Other people's motivations are simply alien to you.
This is why Obamacare was a sinister effort to completely remake American society, rather than subsidized private health insurance. Because if the Teanderthals get control of the levers of power, they will undertake a sinister effort to completely remake American society. The Right is unbelievably ideological - though the far Left is, too. The liberal center is much more pragmatic; pragmatism was a defining element of Obama's presidency. But if all you know is ideology, that's what you see in others.
Trump is slightly different, but the model of projection is still very much in play. Trump tapped his employees phones; he will do or say anything that accrues him an advantage from moment to moment; he sees the world through the lens of his own image. And that is how he sees others.
Does Trump believe Obama tapped his phone? Probably, because Trump would've done that himself.