Nothing happened, but it has never been connected to police work. If the police assumed everyone was innocent they would never catch anyone. “innocent until proven guilty” has to do with the court system.
I tend to agree with you about the likelihood of his being caught. But I don’t think the harassment is based solely on the profile. Hatfill is one of perhaps 100 people in the world who are thought to have the expertise to produce the anthrax. He had a job designing some sort of related material. He had an interest in the subject - he wrote a novel about biological warfare. He had a connection to some right-wing South African group. He failed lie detector tests. Bloodhounds had a strong interest in his house (& that of his girlfriend). He had been denied government security clearance. Each one of these facts are weak on their own, and even all of them together are very far from being conclusive. But they are suggestive.