You’re linking to a left-wing organization. But you’re ignoring the fact that, just two years ago, a decisive majority of Chilean voters (55-45) voted in the center-right, pro-market party and Presidential candidate:
https://www.theguardian.com/world/2017/dec/17/chileans-cast-...> Months of campaigning exposed deepening rifts among the country’s once bedrock centre left, an opening former president Piñera leveraged to rally more centrist voters around his proposals to cut corporate taxes, double economic growth and eliminate poverty in the world’s top copper producer.
The current President ran on corporate tax cuts and won. The majority obviously did not do so under the belief that Piñera was going to nationalize the pension system. The protestors evidently are mad about that.