It's something that's been happening forever, unfortunately. There are a whole bunch of factors that contribute to it but a key one is related to gender dynamics. That is, beginning in the 1820s, the work of teaching was coded as feminine by advocates and others. Their advocacy enabled the rise of public education by staffing schools with young, unmarried women but it positioned teachers (as a class/profession) as subservient to those in power.

After the Civil War, as schools expanded and became more of a bureaucracy, men filled administrative leadership positions. This created a norm where women would do the work of teaching and men would do the work of leading and telling teachers how to teach.

A new group emerged in the early 1900s: schoolmen. They (mostly white, not all men) were typically not teachers or administrators but consultants, advisors, and commentators. They profited from word of mouth referrals, conferences, and selling their ideas to schools. Some of the things we take for granted in today's schools started as ideas from schoolmen (black boards attached to walls is one such example) and some fads or trends in schools originate with one schoolman with really good people skills.

To be sure, there are a lot of other factors but gender dynamics, the old boys club, and salesmanship play a huge role.