In last 15 years we have repeatedly seen that if you have money and/or the right motorsport background and start early it is almost guaranteed to get to somewhere around 5-6th place in WRC cars. (Matt Wilson stopped here, Novikov also comes to mind, Greensmith and Katsuta here atm).

But then the number of drivers improving on that drops drastically.

The first very difficult step is being able to fight for podiums on pace. (Rovanpera is somewhere around here now, Suninen also)

Afterwards another huge step is fighting for rally wins ( Mikkelsen here atm) and the next is having real shot at championship (Latvala finished somewhere just short of this, Hirvonen finished here).

All the listed driver names have had some of these advantages. But interestingly none of the champions since 2000 or so fall in this category imo.