Industries Where Dumbasses Get Rich

Have you heard of crypto ?

Crypto and real estate. 

Construction contracting.

What I take away from your question is you believe that getting rich is predicated on being smart and I think that's wrong. I work with plenty of people that are super smart and not rich because they don't like taking risk. So many people have become rich making drink brands (see isles at Whole Foods) and boutique cafes (see Cha Cha Matcha, Blue Bottle). It's all about being willing to take risk and know how to market yourself and the good/service you provide well. I think real estate is a silly take because while those people may seem dumb compared to a derivatives trader, they are very knowledgeable about real estate and know how to take risk. That being said, contractors and building products adjacent businesses come to mind. 

inheritance 

Car dealers

Content creators and influencers. Some are smart for sure, and I suspect a large amount may secretly be intelligent but spread misinformation or slop content they know their audience will like (Grant Cardone, Shelby Sapp, etc). However, a lot of the big influencers are definitely stupid but lucky. Kim Kardashian and Clavicular come to mind.

Politics, as long as you have a weak moral code. You just need to be smart enough to not get caught doing anything explicitly illegal, or at least shill hard enough for someone smarter that will help bury any controversies.

This does not at all count as an industry but drill or gangster rap - you can get a nice gravy train if you upload YouTube videos where you self snitch over a mid studio beat. Say more and more inflammatory things to increase views until you go to jail or get killed by someone else like you. Many die with little to no money, but some like NBA Youngboy, Lil Durk, G Herbo, etc make millions. Watch the linked videos to see what I mean, or look up Pooh Shiesty's brilliant plan to get released from his contract with 1017 Records.

All 3 of these guys are dead now

Dare i say it, but recruiters - the best ones actually can be quite good and make decent money.

I would caveat that a job like finance only really requires you to be 'academically smart', having the right profile, going to a good target/semi-target etc, but that only takes you so far. The technical elements of the role can be intellectually stimulating and challenging, but 70-80% is repetitive with learning as you do

Rich or high income? I know guys who cleared 1mm selling skin grafts last year, I know a guy that’s some regional manager age 28 for some insurance arm clearing 500k/year. Know a guy selling life insurance making 1mm a year, multiple wealth managers making 1mm+ a year. There was another guy I know who cleared 1mm selling SaaS (outlier) at age 25 or 26.  Wouldn’t say these people are dumb, maybe not book smart, but great with people and have good work ethic.