Remember the professor who went boinkers and shot her colleagues? She possesed competence and was really stellar in her research. They did not grant her tenure because she was perceived to be a bad fit. The department was not looking for stellar scholars; they were content with mediocrities doing meddling research.
When I interviewed at a state university, an old dean took be aside and told me: "Son, the most important thing in making tenure is your relationships with your colleagues and the chair." He told me it was important to make relationships outside of my department because such persons might end up on your tenure committee. If they don't know you well, they will base their decisions on hearsay, intuition, rumors, politics, etc.