I think there's certainly an element of tall poppy syndrome here. Windows, for example, used to be targeted because its security was a complete joke until quite late in the XP era (SP3 IIRC). But there's always been, and still is, and element that it's targeted because it's a big, juicy target.
A huge portion of the desktop and server market are running Windows. It used to be almost all Windows, at least on the desktop. Nowadays mobile computing has become far more important so Windows doesn't have the end user dominance it once did, but there are still a huge portion of end user devices running Windows.
Same on the back end: it's just a big juicy target, and the bang for buck that hackers get from it is huge given how prevalent it remains in corporate and government environments.
A huge portion of the desktop and server market are running Windows. It used to be almost all Windows, at least on the desktop. Nowadays mobile computing has become far more important so Windows doesn't have the end user dominance it once did, but there are still a huge portion of end user devices running Windows.
Same on the back end: it's just a big juicy target, and the bang for buck that hackers get from it is huge given how prevalent it remains in corporate and government environments.