How are my AM lights finding ground?

I installed a pair of ditch lights, then installed a lightbar on my bumper. The bumper light is an unknown brand or specs. My best friend had it in his garage and no use for it so sent it to me.

I ran a new fuse block to/from directly the battery. I ran a ckt for each light through a relay connected to switches in "ground trigger". So the switches in the dash are only wired with a ground and then grounded under the driver kick panel.
The ground for the lights/devices is run back to the fuse block. the fuseblock is then grounded.

So, I decided to check this unknown lightbar for amp draw to find out the specs. Simple enough. I grabbed my multimeter and pulled the ground off the fuse block.
I check the lights, and damn, they lit right up with the fuseblock ground disconnected.

The lights and switches are working as designed. My battery is just fine. Why is it when I pull the ground from the fuse block, the lights still light? The purple line is where I broke the ground and wanted to put my MM inline to check.

TIA

 

Beats me?
Maybe the negative wire for the lights is a redundancy for the mounting hardware?
Could it be the mounting hardware is a ground too?

 

Weird. The lights are typical Amazon lights, with a red and Black wire. The negative wire from the lights are going to the negative on the block and the block negative is going to the ground.

I have not started pulling the grounds off the block, but I guess thats the next step.

 

Perhaps this -^^
Try removing the light from any connection to the truck and just use what should be the ground wire off the light?

 

My guess would be case ground.
It's not that unusual.