It’s the only CMS that runs on a classic AMP stack which is still the standard with cheap web hosters. And since everyone and their dog is using it, you can easily find support and ready-to-use plugins for almost anything.
In the car world, WordPress is your plain old petrol car that just runs, can easily be refuelled and you can get anything repaired at every other street corner. That’s why it is still so widespread.
No need for reverse engineering - it has already been done: https://github.com/RhetTbull/osxphotos