the mats should have a plastic grommet snapped into the hole form the top and bottom.
as i recall the bottom part that snaps onto the peg is smaller than the top part.
did someone snap the grommets in upside down ???
or is the bottom side of the grommet missing?
the peg could have been replaced also with the wrong size peg?
somewhere here on this site was a long discussion about how hard it is to find the correct grommet / peg replacement parts,
if the parts were messed with on your car , that could be your problem.
when i bought my XLR one of the grommets was pushed out of the trunk divider, luckily it was in the glove box.
i was able to pry apart the two halves with a metal putty knife and mini screwdriver, and re-snap it back into the correct place int he trunk divider.