Ill disagree, I still believe it is because Windows is far less secure.
Linux == 98% of all super computers (Top 500 List)
Linux/Android == 74% of all Mobile devices (Gartner)
Linux/Android == 61.9% of all Tablets (Gartner)
Linux == 78% of all internet Servers (Security Tech)
Linux == 28% of mainframes (Gartner)
Linux Desktops == 1.65% (From Gartner as the total number of systems shipped with Linux pre-installed) up to 20% depending on the source.
That is not even getting into all the routers and smart switches, embedded devices, etc.
Open source and Linux make a very large target with lots of high profile targets. I am surprised that there are not more exploits and the simple lack of viruses should be proof enough that linux is far more secure.