It sounds like not enough evidence was there to do anything more.
But yes, you highlight the problem.
Some times there is some evidence, they act on it, but it turns out that person is doing nothing wrong - and we cry out that the police/FBI/Government are abusing their authority.
Some times there is some evidence, but not enough to act on, but it turns out that person IS doing something wrong - and we cry out why didn’t the police/FBI/Government do their job?
It is a damn if you do/damned if you don’t sort of thing. And while I am quick to call out police and government shenanigans of abuse and over reach of authority, I do cut them some slack on grey areas because this sort of thing is rarely cut and dry. The whole police/crime drama where at the end the bad guy gets caught and either confesses or has 100% air tight forensic evidence is largely fantasy.
