I bypassed the fuses, and the open sprinkler pi appears to be working now. It is drawing about 300 mA when a valve is open.
Summary:
I believe the primary cause of the problem was a bad power supply.
I replaced the solenoids, but I don’t think this made any difference.
I shortened the 100′ cable by 48′. I think this extra length might have helped trigger the bad behavior of the original power supply.
I replaced the AC power supply.
I removed the power supply from the USB C connector. I believe that having this power supply defeated an accidental safety behavior. If something shorted one of the solenoids, it will kill the AC voltage. If the USB C power is not there, this will cause the PI to reset, and shut off the shorted solenoid. If the USB C power is is place the Pi remains powered, and the solenoid will remain on with the likely result of the triac burning up.