Clark: What happened Lex?

Lex: The two theories seem to be... I either ran the plant into the ground
through incompetence, (because of that?) or did it deliberately so I could go back to Metropolis.
Clark: Your dad already offered you (a long time ago as in before?)
a job in Metropolis. Just tell people the truth.
through incompetence = not able to do the job, not good enough
already indicates action in the past, but not necessarily 'a long time ago'.
Thanks, Philip!