Who are the equivalents of olympic champions for soft/social skills? What occupations do they usually hold?

I would expect to find them among lawyers, marketers, fixers/facilitators/deal-makers. Red-pill people probably want to be there, too :-/

What is the present day equivalent of the Byzantine courtier

A political operator, playing the usual games in the corridors of power.

the best performers in the cynical management of people so they further their goals?

Steve Jobs was said to be very very good at this.

occupations which select for such abilities

Salesman is the obvious one. There are LOTS of books on how to Win Friends and Influence People :-) starting from the Carnegie classic. Check out your local B&N or browse Amazon.