Actually, he did. Bonnie (Kat Graham) performed a protection spell that unintentionally linked him to April (Grace Phipps). The human girl suffered the brunt of Kol’s attack, nearly dying in the process. But without the witch’s intervention, we’re pretty sure Shane would’ve been one dead human.
Or maybe he’s a witch who lost his powers. He certainly seems to have some connection to Silas, and some viewers have suggested they’re the same person.
However, we think he’s just a lonely guy whose wife and son died who would do anything to get him back — though we’d call the prof closer to crazy than just “passionate.” You know he’s heard those rumors that Silas will destroy the world and is just choosing to ignore them.