When paul started his job, he developed a close relationship with richard, a senior colleague. richard paul succeed in his job, and with richard's , paul was quickly promoted. according to levinson, richard

I believe the answer is:  acted as a mentor to Paul

The title of mentor could be given to a more experienced person that give you direct help in achieving your goals.
For example , In company setting, a mentor could be another employee that get into the business before you do or an old timer that has retired and decided to dedicated himself to aid others with similar career path.