Technical details aside (which I will concede was not fully accurate from what I wrote), do you see my overall point, from a broad, general-user-vs-tech-nerd perspective, which you essentially just proved?
The other point was not whether *nix COULD be a replacement for Windows and gaining 70+% marketshare, but presuming that it already did through whatever means necessary for the sake of the rest of this hypothetical discussion.
Linux could easily take the market share right now, if commercially produced products and OEM would support it! With little support with OEM's it will always be stuck in the geek category. Adobe is one good example, pre-online based Photoshop, has been asked to support Linux system for over a decade and they choose not to. Even with the online version they choose not to support it. If a product like GIMP could make inroads in schools it would do very well but we have a system that wants to teach students something a vast majority do not need but are made to think they need.
I don't know if it is still true but MS licensing to OEM's used to be very restrictive on what the OEM were allowed to do as far as OS installations.
As far as the OP, yes Linux would definitely be a larger target if the desktop share was greater. It is already proving out in the server market where there is ransomware targeting Linux web servers already in the wild.