Here's the theory.
My dryer is quite old.
The leads for the thermostat heater being plugged into the blower box thermal fuse may be thus.
When the thermostats die, they take out the fuse.
The thermostat and thermostat heater are part of a variable heat system in my dryer. What the little heater does is trip the thermostat. It's just a bi-metal switch in there. What this does is cycle the heating element off and on giving allowing the temperature to be adjusted.
My theory is the thermostat croaked, and took the thermostat heater and fuse with it.
Previous owner bought a new thermostat, but not the heater. He had wires left over and plugged the heater leads into the dead fuse and when things still didn't work, twisted the ends of the fuse leads together. Function restored! All better!
Bypassing that fuse is a common repair I've seen now.
It's also possible that the fuse was bypassed first and the heater was omitted later and the leads were just parked where it was handy.