Cargill Process Engineer interview questions

Initial interview at a college job fair. Within a week was offered another interview in Minneapolis location. Interviewed with about 20 other people. Had lunch with interviewers afterwards. Everyone was very nice and polite and fun to talk to. Two days later I got a call saying, "thanks for the interview, everyone had nice things to say about you, however we don't think you fit in any of our open positions." So I have no idea what went wrong.

cv, followed by phone interview, then assessment center. Very basic competancy questions. Nice friendly staff