Thanks for the question.

If bulb flies (actually its larvae) were the causative agents, one would not have expected much in the way of vegetative growth.  Since you appear to have this growth before they were chewed down, I think that we need to look for other causes.  Still, you might find the following to be of interest:

https://www.gardeningknowhow.com/ornamental/bulbs/bgen/tips-for-bulb-fly-control.htm

I suspect that you seeing damage done by rabbits and/or voles.  Both critters have very sharp incisors and make clean cuts.  Rabbits usually leave some pieces of the stem remaining above ground.  Since you saw that these stems had been cut close to the ground, and since voles are ground-dwelling animals, voles are the most likely possibility.  From my own experience, I know that they love all types of lilies.  Controlling voles can be challenging.  However, they have rather short life spans so they don’t last too long.  Take a look at the following for ways in which you might deal with voles.

https://extension.umn.edu/planting-and-growing-guides/vole-damage

https://homeguides.sfgate.com/rodent-protection-lily-bulbs-32951.html#:~:text=Lily%20bulbs%20make%20a%20delectable,%2C%20barriers%2C%20traps%20and%20baits.

https://www.longfield-gardens.com/article/How-to-Protect-Flower-Bulbs-From-Voles

Good luck!!