Why does a Venus Flytrap’s biology allow it to eat flies,which are supposed to be it’s predators?

Question: Why does a Venus Flytrap's biology allow it to eat flies,which are supposed to be it's predators?
- Keywords:
  biology,
  fly,
  predator,
  venus flytrap
Asked by musketeer231 to Freddie on 11 Nov 2016.
- Freddie Morrison answered on 11 Nov 2016:
  
  Flies don’t eat venus fly traps they just want to eat the sugar it makes. The Vunus fly trap wants protein (if it is on empty soil) so eats the flies to get it!

Question: Why does a Venus Flytrap's biology allow it to eat flies,which are supposed to be it's predators?