A light fixture in a bedroom closet blew a bulb and upon opening the fixture I found water/moisture dripping form the conduit. The ceiling conduit goes into the attic and it is very cold and dry this time of year.

There IS NO SIGN OF WATER IN THE ATTIC. Everything is bone dry and no water marks are seen.

The conduit goes above the insulation and branches off to a bathroom in one direction and a wall switch in the bedroom and then on to a second bathroom in the other direction. When the lines enter the bathrooms they first go to inwall light switches and GFI outlets before going on to the ceiling fan vent for the bathroom. There is no sign of moisture behind any switch or outlet face plate in this series. Both bathrooms have vents on this line wich have no tubing venting to the outside. They both just vent into the attic insulation, ( I realize this is improper). Showers in this house are often long and hot and they usually had the vent going during the shower.

The conduit between closet light and the wall outlet in the bedroom seems to be the source of the water.

The issues is moisture/humidity from the bathroom is migrating up into the conduit, and this moisture is condensing in the conduit.

After insuring there is no low spot in the conduit that water has collected, both ends of the conduits should be sealed with a putty to prevent the moist air from getting into the conduit.

Electricians normally use a putty called Duct Seal, it is moldable, and never hardens, which allows for easy removal of wire later on.

You might consider adding insulation on or around the conduit in addition to sealing the ends. I definitely sounds like your problem is condensation.