Using the /effect command levitation on entities will not get the same effect as the player.

What I assumed what will happen is effecting an entity with levitation (time) 255, so it'll hover.

It had the same affect of levitation with 127, flying away to the sky.

Steps to Reproduce:
1. Summon any entity apart from yourself or another player.
2. Type /effect @e[type=(entity name)] levitation (time) (above 127)
3. The entity(s) will have the effect of levitation with 127.