With the different flavors of Linux, the varying configs, and uses, etc. it would be a less-likely target because it's overall much easier just to infect one of the numerous Windows computers or servers in a corp, then pivot to the other machines within the network from there.

Whether targeting public facing Windows servers, or the employees' own desktops, it's easy to see why Linux would be more of an afterthought. Windows devices massively out number the number of daily-use Windows devices, which also increases the opportunity for attack.