It evolved direct development because, in the specific conditions of the Roraima summit, individuals with slightly more complete embryonic development had slightly higher survival rates, and over many generations this incremental difference accumulated into the complete elimination of the free-swimming larval stage.

The Heliamphora pitcher plants did not evolve carnivory because they “wanted” to eat insects.

They evolved it because, in the nutrient-poor acidic soils of the tepui summit, individuals with slightly more effective mechanisms for trapping and digesting insects had slightly more nutrients available, and over many generations this incremental advantage accumulated into the elaborate trapping structures and digestive chemistry of the modern pitcher plant.

This is how evolution works.