I haven't heard any good inside information on it.
It's possible Lambert was waiting to see if he got the HC job at Marshall. I believe he interviewed for it. Marshall went with an outside hire, so at that point Lambert was available for our job.
My other thought was that Brohms first choice was Clayton White from WKU. He ended up going back home to South Carolina, so Brohm had to have a Plan B.
Mike Elston from ND had his name mentioned a bunch. I wonder if was heavily in the mix.