The dam that has finally broken is the Progressive control and dominance in the media.
The reason is simple. The Progressives controlled the media, for all practical purposes, for about 35 years, 1960 to 1995. It was mostly semi-consciously through dominating leftist ideology through that period.
After the Republican revolution in 1994, their belief that everyone thought as they did (or at least a very strong majority of “people that mattered”) was shattered, and they became openly, aware, partisan hacks. They deliberately traded credibility for political power. That lasted another 20 years, but their power was waning, with most of the power being focused on national elections for president and senators.
With the election of Donald Trump, their credibility account has been shown to be bankrupt. With social media and alternatives to the establishment media, such as Fox and talk radio, they no longer dominate.
Because they no longer dominate, the scandals they routinely were able to spike, cannot be spiked any longer. The dam has been broken. I do not think they will be able to stem the flood.
I don't know where history is going to pinpoint the start of progressivism, but in my mind it started around GWB election, not 1960. Pre Progressives were just called liberals, and there used to be some democrats, now it's just progressives and liberals.
Then there was the Republican counter-revolution of 1995 when they realized - yeeehaaa! - that they didn't need to keep Gingrich's contract with America and set about getting their fair share of the pork - and lookkee where we all are to day.