Before the internet, centralized places of knowledge were needed, and you'd need to attend that place to find said knowledge. Think about how access to music caused the price of albums to drop. Education had not seen a similar dip in cost even though the supply is 100 percent saturated. There's a dying class of professors who got in while tenure was still a thing that paid probably 1/10 of the cost for education kids…
Nope, liberal arts majors earn as much as professional and pre-professional majors. https://www.chronicle.com/article/How-Liberal-Arts-Majors-Fa...
And like the OP said, there is now a glut of humanities degrees higher than the demand for positions.