I did things in the exact opposite fashion as you, but found the exact same thing. However, I started at 25nl, and with the $11 MTT's (PP $1000 guarantees), and the same holds throughout.

Im pretty sure of the cause too. If you're the average donk, sitting at home watching GREAT players like Moneymake, and you wanna play too, would you rather spend your money at some boring-[censored] cash table, or an exciting multi-table tournament?