It could be because Minecraft is the only CAD system that includes a sword as a standard tool. It could be that at €20 (or free on a Raspberry Pi) Minecraft is very affordable.
Yeah, yeah, yeah. I know. Dimensioned drawings, FEA, subtractive geometry, meshes, tolerances. A whole lot of really complicated stuff that grown-up CAD systems need to do that Minecraft can't do.
Can't do right now, that is. But who has the user base? People are doing real CAD with Minecraft right now. So it's not a question of if Minecraft will disrupt the CAD market, it's a question of whether Minecraft will disrupt CAD enough to be a dominant player there.
Minecraft has a Python interpreter. Not some ratty ad-hoc scripting language, a full-on programming language. Not easy to get at on all platforms, but it's there, with a 200-page textbook. And a sword.
And Minecraft has collaboration tools built in. And mobile. And monsters, of course, but you can turn the monsters off. Which would you rather have: (i) a collaboration tool 40 million people know how to use that actually works across the internet but lacks some key features, or (ii) a metastatic drafting tool with no collaboration features built in, and a totally separate collaboration tool you'll never use because you'll never get everyone you collaborate with to have it, and even if you did, it would cost a fortune and require a whole IS team to manage?
The war is over. The games won. The sword is mightier than the ribbon.