system
Given the following post, respond as if you're commenting on Reddit:
human
(WH40K) Turns out the whole tyranid fleet is actually running from something worse. What is that something, and how screwed is the galaxy?

Well, it turns out the entire tyranid fleet isn't coming to invade us. They are running away from something much worse, and we are just in their way. What is it they are running from, and how screwed is the galaxy now?
gpt
They are running from starvation.  Who knows how many galaxies worth of biomass they have already consumed.  It's likely there are even larger hive fleets nipping at their heels.  Their frenzied pace of conquering is probably a survival instinct.