Because that's his ambition. When Superman interfered he went for another shot for his ambition.
Likle the man who wants to be President and fails and then tries again until he succeeds. Quite simple to understand indeed.
Granted, and I can understand that. My gripe was leaning more towards the creative decision of what to do with Lex. The fact that we have a new movie meaning to relauch a franchise, yet the antagonist's goal hasn't changed in the two decades since the first Superman film. It was a rehash that didn't bring us something new.
It does have to work on the first place and then when he has the land he will start getting the money. Land and money as an ambition makes sense.
But there was no real explanation of what the hell he was going to do with this land. If what he said was true, most of the world's population would be dead, and then he would be left with a barren island that would have no social, agricultural, or economic backbone. And in terms of keeping this new land, all he said was that he would have "advanced alien technology" but I would have preferred to know exactly what he meant by that, because all that the movie showed us was that he had a bunch of crystals, that as far as we knew only grew things like the fortress or that island.
She is at first on the movie. Then I guess it's plausible to assume he recalled having sex with Superman before he left and quite close to the day she had sex with richard. Suddenly 2 and 2 makes 4.
Well in this case, I did get to read an exact quote from Singer. When asked about why would Lois remember sleeping with Superman, but not remembering his identity post Superman II where these events occured (which from watching "Superman Returns" is what's implied) Bryan said (and I'm paraphrasing here,) "Oh, I ignored that part...I just assumed she remembered sleeping with him."
And I stand by my comment on the sloppiness of the movie. Unless changing it to apathetic writing makes it better. Nothing was explained in a satisfactory way. How did Lex know so much about the Fortress? It did look like he's been there before...but if he had, then why didn't he do what he needed to the first time there instead of revisiting it now? If he hadn't, then how did he learn what he knew about it. They don't tell us any of this...just a simple remark, "You act like you've been here before." The extent of his plan, the Lois/memory thing, a pointless flashback scene that was just tacked on to the film...nothing was expounded upon in a satisfactory way, leaving us with what honestly feels like an incomplete film.