a not insignificant portion of generic weird mediatek chipset android phones come rooted from the manufacturer, because the OS is built with a root/developer configuration. This also helps malware like this spread on the sub-$80 android phones sold to non technically sophisticated users in the developing world.
I remember reading something about mediatek based phones saving on the BOM by utilizing virtualization on a single SoC to run the baseband RTOS and the Smartphone OS.
Until you get bugs like "3D games lag when in fast moving car due to constant cell handovers" and "4G doesn't work at the same time as playing a 1080p60 video, so netflix/youtube are broken unless on wifi".
