My best guess has been that there's an oversupply of incompetent "developers" trying to play the numbers game, doing enormous numbers of interviews hoping they'll find a company that will hire them anyway.

If incompetent developers do 100 interviews per job, and only last at jobs for 6 months before being fired, and competent developers do single-digit interviews (or 0, getting hired through networking) and stay employed for years at a time, a very small proportion of bad actors can be severely over-represented in interviews.