As a Canadian, this has always seemed weird that they were Canadian victims too. Sure Canada is a US ally, but there's been a pretty big difference in policy toward Cuba between the two.
So I don't even see any motivation for the Cubans to have instigated an attack at all and myy best guess would be something done by North Korea or Russia or some other actor that has been a soft ally of Cuba, but also benefits from ongoing conflict between the US and Cuba, and would also benefit from worsening relations between Canada and Cuba.
That the US hasn't initiated stronger retaliation makes me think they know this to.
It could be deflection. Target apparently random people, so that it's difficult to tell who the real target was.