The premise of the article is wrong. From 2009 and until 2015, the number of CS grads almost doubled and any of those economics majors could have seen that in the graph, even if their essays are "basically bullet points" and their field is dead simple. They could also have told the blogger that causality might go the other way; Salaries are high precisely because demand is bigger than supply. If (or when) high salaries cause more people to study CS, salaries will drop unless demand rises even more.

So we have a huge increase in CS majors in just 6 years. What could be the explanation for that? I would say that CS has become both more rewarding and more accessible in the last decade.

More rewarding because with better browsers, and with smartphones, you can simply do more stuff. And those who graduated in 2009 started studying just before iPhone, before Google Chrome, HTML5. Long before Tesla and SpaceX were household names, long before we again believed in AI and robots. The field has simply become more and more interesting.

More accessible because of Codecademy, Udacity, Udemy and the rest of the bunch. 10 years ago, learning to code meant reading books that were already outdated when you bought them and spending days in frustration trying to install whatever language you had decided on. Before you did as much as a hello world. Unless your friends knew how to code or you were enrolled at an educational institution you didn't have access to tutors. Today, you can get great tutorials online, and you can learn JS, python and many other languages without the hassle of installing anything. And once you are up and running, there are a plethora of libraries, modules, frameworks and ways of deploying which mean that you can do in weeks what before could take years.