What's the difference between smurfing and deranking on purpose tho?
I mean you are playing in a lower elo in both cases, so why would it matter?
And I don't think that people smurf just to win easily. It's just about having a more relaxed game, like Deagle or Scout only, without caring about losing or about your mates shouting: "Stop playing SSG only, you have 14k$"

And casual is just not the same.