From what you describe, I assume that your pop-up was connected to the towing vehicle and thus was using the auto's voltage to the lights.
If the previous owners selected the right replacement lamps, they should have been safe and should have operated properly on the auto's 12-VDC. I suspect that the previous owner used the wrong lamp.
If the LED assembly and lights are a standard design, then they should never have been in danger of burning out.
This leads me to suspect the pop-up wiring. First of all, pop-ups are notorious for having poor ground connections, so make sure the light fixtures are well grounded, and that there is no corrosion on the ground connections or loose wires. LED lamps are designed to operate on 12-VDC and can work properly up to maybe 14-VDC, but above that their protective circuitry can burn out.
I would also check the DC voltage without having campsite power plugged up.
I do know of one RVer who contacted the LED lamp manufacturer, and they apologized because they had sent them an LED that wasn't designed for the variations in voltage you experience in an RV.
If the lamps are the proper ones they should never burn out, which would indicate a high voltage.