As the article explains, in 2021 there was an archeological survey of an old residential school that revealed it had a mass grave of an estimated 200 children. That sparked an investigation into other old residential schools and dozens of other unmarked mass child graves were found with over 2,200 estimated remains.
Residential schools were paid for by the Canadian government and run by the Catholic Church. Their aim was to forcefully assimilate native children into Canadian/Catholic culture by taking them from their homes and putting them into these schools. The more you read about this school system, the worse it gets. It's definitely one of Canada's worst historical moments.
In response to these discoveries, the Canadian government donated some money to charity, created a new holiday, and renamed some roads. The Catholic Church refused to acknowledge their role in creating these mass graves of children, or even apologize, until a year later and after constant badgering to do so.