3 people interviewed for 1 AO position? Where did you get THAT information... Just doesnt make any kind of sense to me.
Anyway, squeaky wheel gets the grease. I had to wait a few weeks as well, and in my follow ups, my manager WAS on vacation as well.
Exelon seems to have a "if we dont call you, you're not hired and we wont say why". Id, at the very least, push to talk to someone to find out WHY you didnt get hired, and then do what you can to change that. Hopefully you get hired, but Id suggest keeping on looking. These places seem to be finicky...