I can't escape the feeling that whatever happened in Clark's interview is the key to it all. He must have said or done something that Perry or Lois took wrong and torpedoed the interview.
Or - Perry already knew that his star investigator was at Star Labs with some yahoo he didn't know, and when Perry questioned the yahoo (Clark), the moron claimed he didn't know what Perry was talking about and there was no way he was going to work for a crazy man.
It's probably something even more bwaa-haa-haa than than, though. I hope my heart can take the pounding.