It's usually referred to as "blockbusting", and it even has a
wikipedia article. You can still find some articles about it happening today, in some different forms. Just one random, funny example here from some years ago (
direct link): "Thomas Kelaher, the mayor of Toms River, was quoted in a recent Bloomberg News story as saying that Orthodox Jews are trying to buy homes in his town and warning local homeowners that if they don’t sell, they will be the only non-Orthodox left. “It’s like an invasion,” Kelaher told Bloomberg. “It’s the old throwback to the 1960s, when blockbusting happened in Philadelphia and Chicago with the African-American community — ‘I want to buy your house. You’ll be sorry if you don’t.’ It scares the hell out of people.”".