because in the real world, the A crowd is those that were the D crowd as kids...they're the managers, the investors, the doctors, lawyers and such, they have the money and the power. Tides turn..
First of all I won't say the case applys to "all" cos it highly depends on individual. However, there're several reasons behind this.
1.) They're spoiled, when they're in school they can only hear cheers, appaulse and all the good stuff. Once they come to the outside world, they're only one among millions, they're no longer the "special" one so they have trouble to accept the fact and they'll change.
2.) Backgrounds, up bringing and values - was there anyone teach them the correct values in their life. Are his / her parents there to support them or giving them directions when they're lost, if ones has bring up properly he / she can deal with the issues or matters properly.
3.) Choice of peer and friends - did he or she choose the right people to be friends with? Most of the time they hang out with the wrong people they think that "cool" but eventually lead them to big trouble.
Well, now, not ALL popular kids turn into losers. A lot of kids have a hard time adjusting to regular/real life after their glory days in high school, especially if real life hasn't showered them with applause as they were used to in high school. Some even have a hard time adjusting to college life where nobody knows them and what they accomplished in the last four years. It's a real eye opener for them and some crash land and never get over it. Others pick themselves up, brush themselves off, and get back up on the horse to ride another day.
Strange about the valedictorian, but the popular dude just got hit by a dose of reality. They find that the real world already has the popular kid, and there is not an opening for the position. This reality hits them square in the head, and they feel that their life has no more meaning...
When you find out that you're not as all that as you were in your little world, and you didn't do what you needed to in order to take care of things, you just fall to what you described.
Maybe the Valedictorian found that there were people out there smarter than he/she was and they gave in and gave up. Don't know.
Well, I was one of the popular kids at my high school, National and State Honor Society, Miss Music XIII, Miss Deb runnerup, 1st Miss Teenage, and I'm not a loser. I'm currently the assistant to the General Manager of a franchise hotel located in Downtown ATL, and most of the kids I hung out with are successful. Maybe it's just the school you went to. Or maybe it's the fact that I went to school in a different time when there were expectations put on us, and we had to live up to them. I've always maintained that the problem with out school system is that we stopped expecting our children to actually learn anything, but rather just want them to pass "tests" whether they understand what they're being tested on or not.