The big underlying issue is one of the fallacy of hyper-competence that makes all conspiracy theories unravel when scrutinized.
You're assuming that hyper-competence is even required to accomplish such nefarious goals. Things like this have happened throughout history on fairly large scales, even to the point of taking control of entire nations--all done by very fallible people who simply knew what to do at the right times, and perhaps most importantly, used the right ideas. And by "scale" I don't mean the number of conspirators, which is necessarily on the low side--everybody else is either just following orders or is a "useful idiot" (the latter can number and has numbered in the multiple millions).
In other words, the irrational belief that "The Powers That Be" are actually capable of pulling off any of these secret, massive, nationwide (and even international) illicit efforts to subvert and enslave the American public -- when in reality these masterminds can't even seem to smoke a joint, have an affair, or heck, fart in an elevator without embarrassing public disclosures.
That's because in those cases there are people involved who stand to gain from exposing the perpetrator, or involve things of an unmistakable nature that are caught on camera or witnessed by accident, whereas conspiring with a few other powerful people who have the same goals in mind can easily be done in secret.
Did it require god-like infallibility and hyper-competence for Adolph Hitler (yes, I went there, but it's an extreme case, just like your hyper-competence requirement), an elected official, to seize dictatorial power over all of Germany and turn it into his war machine for world domination?
Or at the other end of the scale, were the three Cleveland kidnappers in the news lately hyper-competent in being able to do what they did for so long? Somebody probably caught them farting in an elevator at some point during all those years, but they still got away with enslaving three women, and even their longtime neighbors didn't have a clue (until recent events)--they believed that one of those criminals was a nice, respectable man who lived alone.
That said, sometimes what you do doesn't even have to be so secret, as long as those who see it can't convince others or do anything to stop you. Eventually everything will be uncovered and the bad guys will lose, but not until substantial damage has been done in some cases.
As for what has been going on in the US, I couldn't say whether there are any deliberate conspiracies to undermine the republic for lack of direct evidence, but I do find it alarming that there are so many things that appear to support such an agenda--important general things that affect how people view and think about things, like public education and the mainstream media, including the news, which used to be a decent watchdog over the government, but now very strongly and clearly appear to be supporting the same agenda as one part of the government. Then there are specific things like Operation Fast and Furious, for example. Even if there is no conspiracy, it sure looks
as though there were one, and it's not as if this sort of thing hasn't happened before, with hyper-competence not a real-world requirement (even Hitler experienced failure before he gained power, and ultimately failed in the end, but one could argue that he had an effect on the whole world nonetheless).
Making hyper-competence a requirement for suspicion is effectively like setting up a straw man--since nobody is hyper-competent, then large-scale conspiracies could never happen...except that they have. By no means does what I'm saying validate any particular theory, by the way, and I think it's likely that nearly all such theories are unfounded, but then again maybe some are real, especially since sometimes they don't require many real conspirators at all, just an anti-liberty, anti-American POTUS who abuses and tries to overstep his power, with everybody else just following orders or buying into his nonsense.
