It’s cultural and psychological. Policing is an inherently conservative profession because its purpose is to enforce the status quo. So the police including the FBI have conservative biases and view groups like ELF and Greenpeace as radicalized, while an abortion clinic bomber (who in fact had a lot of help from their church in executing the attack) is considered by the police to be a lone lunatic.
It’s the same reason that whenever a Muslim does something bad (but non-religiously motivated) in the US the media cries out about how local mosques aren’t denouncing the act hard enough. But when a Christian does something bad specifically for religiously motivated reasons the media concludes they’re a bad apple, and their actions don’t reflect on Christianity at all, even if they’re following the letter of the bible.
It’s really fucked up and is a glaring bias in the system, and as crazy as it seems it does exist.
Not enough people talk about it.