Well I am not a fan of the loser Prime minister but let me address your questions.

1. He is a member of CA and is a prime minister because he as the majority support from CA. Nepal's constiution requires just that. Every major party was responsible for creating such loophole so if you want to put your blames at someone, it has to be on everyone.

2. MaKuNe got nominated to CA due the new system of proportionality. The system was put in place due to Maoist demand as they were just too insecure to go to conventional election and lose out every seat.