Don't forget the other side of the trade --- people write PUTS and take in premium. I'm sure that the 100% runnup in the stock is giving the MM's plenty of ammo to bid at a decent premium to those willing to write.
It's very hard to read into the rationale surrounding PUTS. Someone could also be buying those as a hedge to a long share position.
MNTA has now been rangebound for 6 days in the low 20's ... i think we see some action sooner rather than later.