Iranian Air Force shot it down because it had a lot of IRGC people on board including Zeinab Soleimani. These were Iranian sleeper that had come home for the funeral of Qasem Soleimani and to receive orders for attack from within the USA. Some of the Canadians also had US citizenship. The names of some were fake. Others were just messengers for more dangerous people already in Canada/USA.
There is a war now in Iran, between the moderates who wanted out from under the yoke of Soleimani, and hardliners who want to launch jihad right now. Over 90 IRGC officers have been arrested by IRGC intelligence, following the pattern shown in the UK where MI6 cleaned house, and in the USA where the CIA has been ejecting rogue elements or terminating them.