Who was Carlo Acutis? 15-year-old teenager canonised as Catholic Church's first 'millennial' saint

Acutis was just 15 when he died from leukaemia in 2006. His canonisation took place alongside that of another young man, Pier Giorgio Frassatti, who died in 1925 at age 24. Who was Carlos Cutus and why was he called 'God's influencer'?