Why was Croatia's 103rd-minute equaliser against Portugal ruled out?

Croatia's 103rd-minute equaliser against Portugal in FIFA World Cup Round of 32 was disallowed after VAR found Mario Pasalic to be offside during the buildup to Josko Gvardiol's goal. Pasalic was not offside when original cross was delivered, but Igor Matanovic's faint touch created a new offside phase. FIFA’s Connected Ball Technology, a Snicko-like system, detected the touch through VAR.