This has been on the radar of colleges for 15 years. The 2008 recession and general societal uncertainties of the past 10 years may have exacerbated the problem, but we've known it was coming. I think the additional option of virtual courses and degrees will also increase the pressure on small schools.
But seriously - many of these colleges that have closed recently were under 500 students enrolled. That's basically like a small private HS. Headlines are written to look dramatic (100s of Colleges threatened to CLOSE soon!!!!) But the actual impact on higher education isn't as dire. Yes, there are going to be fewer students. Yes, colleges and universities are going to have to adjust offerings as societal needs and wants change. But that is the basic economics of a capitalistic system. I don't see that this is some sort of crisis, but it certainly is buyer beware for students.
And for information - the current US population pyramid:
https://en.wikipedia.org/wiki/Demographics_of_the_United_States
Baby boom peak is at 60 years old. Echo boom peak (Millennials) is at 30 years old. While there is a dip after 2008/9 in children born, I think the bigger issue is the population drop-off right now for ages 5 and under. That is Millennials delaying or foregoing having children completely (for various reasons). This is going to have a bigger ripple effect economically than just college enrollment, and I think it is overlooked right now in economic circles.