Sorry--Not the case.
Don't forget that while Windows has the majority of the user desktop market, Linux pretty much rules the datacenter and backends of many commercial/govt enterprises. The data Linux runs on/protects is MUCH more valuable than anything a desktop user may have.
While the user base may play a small part, it is not in fact the reason why Linux is more secure. It is more secure due to initial base design.
Windows started off as an app sitting on top of DOS. DOS itself was a single-user OS as it was designed before networking was a large concern, and before the basic end user even knew about networking (yes, networking existed, but was largely confined to educational institutions and commercial applications).
Due to the desire, or need, to maintain backward compatibility MS continued to build on that initial design philosophy. I'm not saying it was wrong, or bad (at the time), but it is what happened.
Linux, OTOH, was designed later on after multi-user systems were much more common. Given this different initial environment, basic design is a LOT different, with most decisions based on the multi-user aspect of the OS.
That is the main reason Linux is more secure. It's still not totally secure, but it is more secure.
Yes, I am very aware of the history of Linux and Windows and also that Linux dominates the server market. I have mentioned many times previously that I setup nearly all of my computers to dual boot and that I use Linux for home server duties.
The types of malware designed to steal information from servers is not typically the same as malware designed to steal information from or screw up people’s personal desktops or laptops. The goals are different, the environment is different and the tools are different.
I also acknowledge that you are much more knowledgeable about Linux than I am. I nearly pinged you to this thread along with dayglored this morning; I was not sure that you would be interested.