Isuzu used to use a single voltage regulator for the temp and fuel gauge on Chevy LUVs. They probably continued the trend, so the power for both would come from the same source. In the LUV the regulator was integrated into the gauge panel, not sure where it is in the troop and my shop manual is not handy.

Point is, it makes sense to me that both would get power from gauge reading from the same source, so a single loose wire could take them both out.

"Time and tide melts the snowman"