i think it's probably so popular because it's clean, easy to read, has very solid inheritance structures, and a lot of good built in functionality. it's just easy to be productive with python. the documentation is also pretty good, although i think php documentation has it beat wrt implementing things (lots of good examples and stuff).

i think all of the things listed in that pycharm seo article are emergent from what makes python popular, rather than what makes it popular, except for #3.