Quitting job(일을 그만두다)

One of my best seniors in my company, Mr. Hyun, quitted his job and moved another company. I don't know exactly why he quitted his job. But i guess he couldn't feel good and stay motivated any more as a member of this company.
I just guess that's because he wasn't allowed to take a MBA course in Missouri MBA school. Our company has an overseas MBA training program. They usually pick one or two member and offer them a partial scholarship to help them take that course without a tough financial problem. He was very good at his work and has an amicable personality. So every co-workers around him had no doubt that he would be picked. But sadly, he was eliminated after the screening. Though there were many applicants who wanted to have that MBA program, Nobody really expected he wouldn't pass the screening.
One thing that is hard to understand is they picked one of his workfellows who wasn't expected to be picked at all. I admit that he is also a very good , dedicated, loyal one. But most of the people just knew that it wasn't his turn. In my opinion, this isn't the way things are supposed to be. He surely felt unappreciated and became frustrated, and finally decided to leave.
Right before he left, he said to me and my workfellows, who joined the company at the same time with me, that he will go to America and work in one of the overseas corporation of his new company within two months. That would mean that we should have a farewell drinking party all together for him as soon as possible before he goes to America. I feel quite sad that he leaves us. But I believe he will do a great job in his new life. I wish him the best of luck with anything he does.