There's plenty who haven't made good money. However, the primary assertion is that the technical architects make all the money. They tend to get good pay, but there's plenty of developer jobs around that pay well above average salaries without being architects.
The downside for Machine Learning is trying to communicate why what you're trying to do is hard, and make people understand what you can do (as well as can't do). Given the limited understanding of statistics in general, it's a challenge to get people to move from the Operational business information systems that provide basic dashboards and KPIs on to Decision Support systems that can help with future planning and higher level decision making. Both are valuable, but the former is much more commonly used than the latter.
All that is focused on business operations, though. It ignores that the last 15 years have seen huge improvements in the state of the art for driver aids (and partial autonomy), speech and image recognition and many other areas, to a point where we assume that Facebook will recognise our friends in photos better than we do, and that we can ask Alexa to play some obscure band and it will (generally) understand what you asked for. In a noisy room, even. These are the areas where people can see the potential, not business planning.
Those are also the areas where the architects who don't understand AI can't help much. They can't really help turn your also-ran system into one that has an edge over the competition. There's some pretty serious knowledge requirements for architecture planning, too - scaling to handling streams of data that you can't reasonably store.
The point is, though, that if you look in the right places and work hard there are opportunities in many niches, and well paid ones in all areas of IT. And if the rates aren't good enough for you, then maybe you need to work at getting on the BBC highly paid list as a presenter instead. But the real money, the big money, goes to those who have an idea (and there are many untapped uses for AI) and who go out and build and sell that idea for themselves, not someone else. They're the ones that make the rich lists, not the architects.