As a rule the FBI simply does not announce they're investigating someone because it can damage the investigation, and because it could unfairly tarnish someone who has done nothing wrong.

The encroachment of political calculus into the Justice Department is not a good thing. Let Democrats or Republicans howl about whatever, the DoJ and other law enforcement and intelligence agencies need to do their job the right way, regardless of partisan complaining.

That has no significance when weighed against the risk undermining democracy and effectively choosing the next President, which is what happened.