Except it wasn't "thoroughly vetted". It was given a 20 to 25 day review according to reports. See post 174 about CFIUS rules.
You may be picking nits based on sloppy reporting. Where "review" is the reporter's synonym for "investigation".
Hmmm....verry interesting information. This is about what Republican Senator King (forgot his first name and state) said today on FOX news. His visible upset about this Port Deal as it is is that he says that he is aware of the specifics of the investigation process involved and that the extent of that investigation was that the Cabinet asked Intelligence if they had anything to report about the company and that was it. (To paraphrase.)
I'm betting that Secy. Snow had a lot of weight on this decision and that there was a larger than usual degree of assumption because of his relationship with the company -- probably by others, too (former President Bush, perhaps).