Computer chess improved regularly for decades before becoming a true threat to master players. Why did it start toppling them in the 90s when it hadn't before? More recently, financial programs have carved out a huge niche of the market that was once dominated by human traders.

Why now? Because the technology is finally competitive with humans across a wide range of tasks. Yes newer, some new jobs opportunities do open up, but they're often jobs that those displaced are simply incapable of doing.