The History Channel has always been something broken. There was a period, in the long ago before times of the 90s, when it was Kenny Rogers doing voiceovers of documentaries on cowboys and the Civil war and all sorts of things with footage of interviews with historians and reenactments of events filtered under something that looked like ol' timey paper, and the lettering done on a Windows 95 film editing program. That quickly gave way to Nazis, Nazis and more Nazis, till it was 90% Nazis. The History Channel was so focused on WW2 that they actually had to have people monitor to make sure they didn't reuse stock footage in programs because that became a problem. Then they jumped from the Nazis to doomsday and Nostradamus and to Aliens and conspiracies. Then came in the reality shows. Say what you will about the "Hitler Channel", at least it was history. And I like Pawns Stars and American Pickers, but everything else is not history, nor is this paranoia junk.
The problem with the History channel is the problem with every other channel: the general public is stupid and easily exploited and begging to be exploited (despite their protests that they aren't). So people may piss and moan about reality shows and space aliens and how this isn't what they want to see, and then go watch it, but the documentaries they say should be there, they don't watch. It's the driving force of Capitalism; give the people what they are really going to want, not what they think they should want. That's why all channels have lost their dedicated niche, and have gone stupid and exploitative.
There does exist a saved History Channel: it's called PBS.