Why Is The Queen On Canadian Coins?

By GovMint :

In Canada, the presence of Queen Elizabeth II on coins has been a longstanding tradition, symbolizing the country's ties to the British monarchy as part of the Commonwealth of Nations. However, following the passing of Queen Elizabeth II, King Charles III now appears on the obverse of recent Canadian coins as the new British monarch. The introduction of King Charles III to Canadian currency marks a significant moment in the country's numismatic history and showcases the ongoing connection between Canada and the British Crown.

Older coins bearing the likeness of the Queen on their obverse will continue to circulate and are still legal tender; however, they will be replaced with coins bearing the King's effigy naturally over time. 

Sources Used:

https://www.mint.ca/en/discover/faces-of-the-monarch