That would explain why he pled guilty to an inconsequential crime he didn't commit.
It wouldn't explain why he hasn't followed up on evidence that might enable him to not only get his plea deal vacated, but to sue the DOJ/FBI for millions of dollars.
I suspect his lawyers already know what's up here. I'm just not understanding why Grassley is making such a public show about information that should have been turned over to Flynn's lawyers months ago.
“It wouldn’t explain why he hasn’t followed upon evidence that might...”
The explanation is in the word “might”. Flynn has a deal he evidently can live with, and some hope that his case and Mueller’s entire game will unravel without additional risk to himself. Legal action now would gamble with the future of his family, spend resources he doesn’t have against a ruthless foe with unlimited budgets, and potentially leave him in prison. From Flynn’s perspective, sitting tight might be his best option.
Grassley might want to help Flynn, but his likely motive is to catch the FBI and Mueller in conduct so perfidious that it will destroy any credibility they might retain. If the 302s were forged in this case, how credible are they against Papadopoulos, Page, etc.? The whole house collapses. If it comes out that Flynn is really being punished for undermining the CIA’s anti-Erdogan machinations, that’s a major bonus since it shows Mueller settling CIA scores instead of his approved scope. If pressure forces the DoJ to indict corrupt officials to get him off their backs, he can live with that too.