While the "deep state" idea is only a conspiracy prupoted by right-wing pundits to explain how the Republicans fail to get anything done even though they control all branches of the government, I think there's some credibility to the idea of Rogue faction in the Cuban government or failed surveilance attempts. At least this seems to be the only credible explanation for the fact that Canadians were also attacked
In fact the deep state isn't widely being used on the right to explain the incompetent GOP. The deep state was being accused of trying to sabotage Trump in general, not the GOP in general (was, because most of that early hysteria has died down). The premise was that the deep state disliked the political idea of Trump ushering in greater isolationism, involving pulling back from policing the world and the military industrial complex with its perpetual war machine.
The modern deep state concept has been widely discussed on both sides of the aisle and has been credible for decades, going back to shortly after the founding of some of the very large and powerful US Government institutions, such as the CIA, FBI and NSA among others - all of which have their own gravity in the politics of the US. It's not a conspiracy, it's the inherent nature of government, politics and power. Nearly every government on the planet will have its own active version of the US deep state, only varying in the specifics and size not the concept.
There's absolutely nothing right-wing about it, either in believing it exists (there's nothing to debate there), or being concerned about it (the left and right were both extremely concerned about its use and power during the Nixon era for example).
>While the "deep state" idea is only a conspiracy prupoted by right-wing pundits
That is not true. See Glenn Greenwald or Amy Goodman, for example, both well-known left wing (and also some of the most award winning) journalists-[1].
As I understand it, "deep state" is just a scary-sounding phrase used to mean "unelected career officials". It doesn't mean "shadow government" or whatever you're suggesting might be going on in Cuba.
It is a phrase meant to suggest that those unelected career officials are conspiratorially involved in running things autonomously from the elected officials. I think it's a very partial truth, and agree the scary-sounding phrase 'deep state' probably doesn't really help us understand how things work, in the U.S. at least. The phrase 'deep state' was originally used, I think, about the Turkish government, where it may be more useful/accurate, I dunno.