I suspect cause they are the latest in the range so have slightly better features. From reviews the gx-80 now has the 5 axis stabilising like the Olympus always have had but will work in tangent with the image stabilising built into the vast majority of the Panasonic lenses.
This is something the Olympus can't compete with except for the new 2 grand Olympus big lense.
The 6 stops of stabilising it offers is a real boom for big telephoto lens users.
Plus the sensor has been tweaked and from reviews appears to be on par or beat the Olympus offerings for similar money.
The gx8 offers a 20mp sensor I think which none of the Olympus can compete with. So until Olympus release the new em1 , Panasonic have the better bodies atm. Even then unless Olympus do a firmware upgrade which lets you use the IS on the Panasonic lenses the Panasonic bodies will always have this advantage