I'd like to throw another idea out there: players use MOT to test certain builds, and unfortunately with solo spawns being garbage, the only real-world test is an actual mission with teammates. Yes, the Simulacrum can test too, but only in a controlled environment, and not every player has this area unlocked.
Some players are also simply unprepared for MOT, with the 300% damage multiplier, suddenly enemies are carving out huge chunks of health for their level. My guess is also a lot of new players started playing, or resumed playing, with the new Fortuna update, and we're seeing a lot of