The thing is, WR holders know exactly the maximum speed for each curve. They can perfectly go slower on purpose to save tyres. And if they can do the most difficult lines, that for them just happen once in 10 times, but for a normal racer, its much rare, they can surely do the easier, safer ones.
And since most of LFS comes down to practice, and some talent, (99% transpiration, 1% inspiration, to quote T.Edison) on that combo, they're the ones that practiced it the most.
If one hotlapper has a perfect setup for hotlapping, all the others try to have one too, so it comes down to skill again.