dragging a front brake...how?

Waggy d44 axle swap. Disc fronts. Greased everything before it went together. Bled blah blah blah. Wheeled recently, front left bleed valve came loose on trail seen by little fluid on inside of tire, bled the line real quick and carried on. Been driving for a week and a and a half with no Real issues until tonight. I've had a slight left pull during braking for a while nothing new there even with my old d30. Tonight as I drove home going slow I could hear a hiss with the doors off, no adverse handling. Bout halfway I am having to hold the wheel right to track straight. Pretty significant pull going on. Brake to pull off onto my street and no left pull but not good brakes either. Pedal still felt good. Got home had a real hot drivers front brake, popping and crackling as it cooled down wheel was pretty warm. Hope I didnt cook the wheel bearings and seals. How does a dragging front brake happen? I've drug drums before due to bad adjustment as a kid or forgot a parking brake but never a front... this is a first for me.

no fluid or leaks present.