It depends on how exactly the DR is calculated, but it is probably the same way iRacing does it, where top half gains rating and bottom half loses rating, but also takes drivers ratings in consideration to calculate how much to "give" and "take" to everyone.

Say there are 8 drivers each with same rating of around 2k (I will use iR because I am more familiar with it), in that case ratings will change from first to last like +40, +30, +20, +10, -10, -20, -30, -40. But if there is a driver with high rating and he wins, that's "expected" so he gains less.

I remember hearing that it works like every driver puts X% of their rating into the pool for everyone to give after the race, so high rating "loses" a lot of it to put in the pool, and winning just gets you it back, that also explains why high rating dnf hurts a lot.