The presumption of innocence is a legal principle that every person accused of any crime is considered innocent until proven guilty.

Under the presumption of innocence, the legal burden of proof is thus on the prosecution, which must present compelling evidence to the trier of fact (a judge or a jury). If the prosecution does not prove the charges true, then the person is acquitted of the charges.

My understanding is they never brought the charges in the first place. The supposed online hitman and the victim were both FBI informants. They never filed any charges because it was clearly entrapment and no one was ever in any danger.

The prosecutors later used that evidence as support for their sentencing request after Ross was convicted of only non-violent offenses, which has a much lower standard of evidence. The allegations of murder-for-hire were never tested at trial. They may have evaporated under cross-examination by a competent defense. Our system of justice holds that Ross is innocent of those allegations unless convicted at trial.

It typically means there isn't enough evidence to convict. With the presumption of innocence, it in fact does infer he's innocent of the charges.

It does. Innocent until proven guilty.