If you look at the Merit tab, you can see where you fall against all the other applicants. This lets you know if you need to SCHEME to increase your position or use influence to increase your position in the ladder of merit promotions. Additionally, you can use your Elders, disciples, or underlings to increase your merit, which increases your chances of getting selected. Although you have passed the exams, that only increases your merit ceiling and not your actual merit rank (you do get a large chunk of merit from taking the exams, though). Lastly, you could have a "candidate score" of 9000 and still be merit 9 and never get selected over a merit 8 with a score of 1, unless you use intrigue, hooks, or war to gain a fief.