Right? It's getting pretty gnarly out there.
Without doubt, the most vitriolic manosphere stuff is on the internet because of the anonymity the internet provides.
Hard to say how wide spread it truly is because internet and especially social media index and then cluster content, making it seems like it's very widespread and overwhelmingly profligate once you stumble across it. You've got no way of assessing anything like per Capita, how much the ideology is being adopted, or the landscape as a whole.
What you do know is that they are extremely loud, proud, and obnoxious about this bullshit and they dog female presenting accounts on the internet, particularly if you engage in feminism in any way or are successful outside an "acceptable for females lane" according to these dudes.
So, it you're a woman and you're on the internet, it's not going to be long before you run across the manosphere and need some Pepto quick because of the nausea it inspires.
There's also been a significant amount of discussion regardint the draw and allure this ideology has for young men.
I can tell you, from the men I've conversed with just out and about, through work etc, most men have engaged somewhat with it because I'm hearing the rhetoric repeated a lot, or put into practice. Too much, actually. Far too much.