I've interpreted it as Lex thinking there's not enough time before the invasion and that's why he's driving his staff so hard.

This is definitely part of it too, I agree. Though Lex really should know that people will work quicker and more efficiently when they're happy with their jobs and their boss...

...Oh, Lex, you're not nearly as super-intelligent as you ought to be, and while I know you're being hobbled by the deficiencies of your opponents (couldn't have Lex winning all the time, after all...) it still frustrates!