Yes, bad installer. Dielectric grease was obviously not used. You can get a tube at any parts store, it's the same stuff used to keep moisture out of spark plug boots. But also get some heat shrink about the diameter of the connector. 1. Unscrew connector 2. Slide 2" piece of heat shrink over the connector 3. squeeze a little dielectric inside the threaded portion of the connector 4. screw connector back on, finger tight 5. torque with wrench 1/4 turn only 6. slide heat shrink up all the way to the hex part of the connector 6. apply heat until it molds itself to the connector and the cable.
For even better protection, slide the heat shrink all the way up to the hardware. That covers the hex collar as well, but also means that the heat shrink will have to be cut away if/when the connector must be unscrewed for any reason