Canada didn't have Prohibition to the extent that the US did, which in turn led to the rise and financing of organized crime. All the rest of it fell out of that: Organized crime was violent and ruthless, so people started demanding oppressive laws and harsh penalties to deal with it.

One of the major problems with this is that the cycle is reinforced by law enforcement. You sensibly get rid of prohibition, but then the mob is still around and starts looking for a new source of funding, so you get more extortion rackets etc. Then a law enforcement bureaucracy is created to deal with it, but long-term the mob was going to die out without prohibition anyway and the law enforcement efforts just speed it up a bit. Except now you have a law enforcement bureaucracy with nothing to do, so they lobby to recreate Prohibition in the form of the Controlled Substances Act, which reconstitutes the mob in the form of the drug cartels.

But now instead of saying "prohibition failed, let's repeal it" they say "we need more resources" -- institutions try to preserve the problem to which they are they solution. So the Feds fight any attempts to legalize drugs because it would put them out of a job, but as long as there is prohibition there is organized crime, and organized crime is violent and terrible and a ratchet to ever-harsher penalties.