First of all, Lex in SR was an eccentric business man, not a mad scientist... he had an aggressive, illegal and fundamentally revolutionary business plan... he did not have any mad science going on at all. He was there to make money... period.
Eros said:
the testimony/witnesses of Lois Lane[top level reporter],Richard white [newphew of Perry white], SUPERMAN[who can provide proof], Jason White, among many other things. so no the chances of Lex starting Luthor corp after trying to destroy America is 0 percent.
Lois Lane-- She had NO evidence.
Richard White-- Was NOT an eyewitness
Jason White-- Is a child and can be dismissed easily. Nor is it safe for Lois to put him on stand to testify how he shoved a piano and killed a guy.
Superman-- Doesn't make court dates, read miranda rights (as per the movie) and has no physical evidence that Luthor was involved.
The only thing Luthor has against him is Lois' eyewitness account that Lex had a plan to drown the world... which is rediculous. With no evidence linking Luthor to the island, any lawyer could get Lex off the hook, and with a fortune in his pocket, Luthor can afford the very best.
As far as LexCorp goes, it could be natural for Luthor to create a LexCorp as he bides his time until the next big thing comes along, or to establish a powerbase to make more aggressive comprehensive business moves...
But if Singer decides to have Luthor bide his time some other way that'd be cool... I don't see a reason to turn Luthor all suave and debonair, though, putting on the act for an upscale party would be cool, so we could "see" Post-Crisis lex and at the same time realize acting fufu is not essential to his character...