Most treatments manage the pain. None of them fix what happens while you sleep.
Every stretch, every ice pack, every cortisone shot works on the hours you are awake. None of them control what your foot does for the eight hours you are unconscious.
The plantar fascia shortens every night. Every morning it tears again. That cycle is why plantar fasciitis lasts months and sometimes years despite doing everything right.
The night splint breaks the cycle at the point where the damage actually happens.