Tearing down a slum is not gentrification.

Gentrification is when existing communities that used to have decent if basic living situations get gradually priced out of an area as richer people and their expensive amenities move in. Gradually, as house prices go up and food gets more expensive, people sell and move. It's a slow, mostly voluntary thing, or at least, driven by market forces rather than official mandates.

Tearing down a slum is a much more disruptive thing that instantly displaces a entire community. Although it's unclear what happened to that community in this case and I can't find anything clear about it online (lots of clearly biased articles for one side or the other though).