Sometimes being less fortunate is what motivates people to become rich. The truth is I had a huge amount of stuff holding me back as a child, and still do, but imo that is why I managed to succeed (relatively at least) where others I knew who had similar intelligence and better backgrounds did not. Even in my own family the difference between my sister and myself is massive, she's probably in the bottom 10% and I'm probably in the top 1-2%, yet she has almost the exact same background as myself.
Being poor might just be the single greatest motivator. It also teaches people a lot of valuable lessons for acquiring wealth such as how to save and ration. If you look at wealth statistics in the UK some of the wealthy people here are immigrants or second generation immigrants from India and East Asia which doesn't really fit with this narrative of rich people get rich, while poor people stay poor.
I understand sometimes people are so unlucky that the obstacles in front of them are insurmountable, but I also don't think this paints a full picture. I also generally agree with the article, although I think it's easy to criticise without providing answers. It would have been nice to see some suggestions on how to fix the problem of wealth inequality, because unfortunately many of the popular solutions (raising taxes, expanding welfare programs, etc) could just make things worse.