It’s the social media. A whole lot of social media is dedicated to be an @#$#$%^ version of your particular group. Especially thanks to that one site that makes all those pictures. Even I find the atheist ones annoying, and I am an atheist, just not the kind that needs to be a dick to people. Have your religion, enjoy it thoroughly, just don’t come knocking on my door inconveniencing me with your message and all will be well.
Many of the in-your-face atheists base their entire identity on atheism and on everyone else knowing that they are atheists and in trying to force all others to be atheists, sort of like militant homosexuals. Both groups appear to be totally obnoxious to non nonbelievers because the obnoxious ones are the examples that make themselves know.
Or the Internet generally.
After WWII there was a feeling that in some sense irreligion had "failed," that without God or gods to restrain people, men would become beasts, so atheists were more modest.
That age is over. The feeling has died out. So atheists can be smug again. A lot of people prefer the word "agnostic" just to indicate that they aren't going to go on the offensive against the beliefs of others.