At some point they got ultra aggressive about "duplicate" questions.
Technology changes at a fast pace .. so new questions would get asked, and then closed by moderators and pointed to similar questions that might be 5 or 6 years old and no longer relevant.. essentially ending the discussion on many topics and actively preventing progress in certain areas.
Absolutely this. Later in the piece I learned that one of the mods in a place I'd occasionally asking questions on SO was from my local town and would occasionally attend industry social events. It was amusing to let a few people know and watch the "why did you close that question as a duplicate? That vendor module was only released 6 months ths ago but the duplicate was from 5 years back. Make it make sense!".