Doesn't have to be big oil. Any industry if you work your way up to the top 1%, it's a big pay out. Those secretaries certainly don't make 200-300k a year. Buddy in pharmacy worked her butt off for 10+ years, bought the pharmacy for $5M. Once she pays that off, can easily make $1M a year. Also know a few doctors.
Got a friend that worked as a roofer (build roofs for houses). Started his own company a few years ago and guy makes $1M a month and is expanding. He is literally one of two companies that can do some special roof in all western Canada. Dumb as nails growing up, but he works hard. Now is probably the 2nd richest is my group of friends.
I'm going to have to play devil's advocate here and highlight some of your biases. Your roofing company owner friend is one of only two that can make some special roof in Western Canada, etc. Not every hardworking roofer gets to learn how to make that specialty roof just by working very hard in roofing for a number of years. Certainly the number of hardworking roofers that never got the opportunity to learn how to do that vastly outnumbers your friend by at least the thousands.
By your own admission, there is also a decent chance a number of those hardworking roofers are more intelligent than your friend as well. You attribute his success entirely to hard work, when the luck to have the opportunity to learn that special roofing technique/design was almost certainly a bigger factor. I am sure many hardworking roofers do not get that opportunity. Survivorship bias on your part (though somewhat of a vicarious sort through the lens of assessing your friend). Even then, I am sure there were also roofers that lucked out in having the opportunity to learn that design/technique but couldn't pull together the starting capital for a company, or maybe managed to do it but were underbid by a competitor in the RFP process for a contract.
Likewise with your pharmacist friend who took a $5M loan (minus her principal) to buy the pharmacy. You attribute her success solely to busting her ass for 10+ years, but there are countless very hardworking pharmacists who spend over a decade in that career. Given what I know of the bell curve for pharmacists' (non-owners) income, I am highly skeptical that she managed to pull together the down payment she would need for that size of loan without receiving either some additional financial support from family (luck), or going for that loan during a time when the "price" of capital was very cheap (such as during a time when interest rates and down payment requirements were both extremely low). Also massive luck in timing.
This is all survivorship bias and I advise you to be aware. Just as an anecdote, the married couple (in their 30s) I mentioned are very honest and mindful about the advantages and massive luck they had. Her parents consist of a successful retired engineer that keeps getting pulled out of retirement to consult for big business, and retired head of a government news broadcasting corporation. Obviously raised very well, educated very highly, and with an insane work ethic that fit well with a big 4 finance consulting career before moving into buy side (asset management for massive pension funds, etc.). Also formerly worked for literally some of the most well known American and British banks you can think of in high end finance roles. Finished her CFA in the middle of her career so far. She went to a literal top ranked uni as a finance and accounting double major, and her parents funded her MBA at a top 10 ranked American business school. Again, hard work obviously played an important role, but also the luck of being born into the right family who could fund her education and teach her the importance of that work ethic to begin with. Good role models. And not to mention the genetics for high intelligence. That's luck too.
The husband was a STEM grad of a top 5 ranked American uni (Ivy League), openly acknowledging that he was blessed by his family genetics with a much higher than average intelligence, and much faster than average ability to pick up new, exotic, counterintuitive, and complicated concepts/problems. Started at the lab bench and worked up into program management. Both of them had to outcompete countless other hardworking and very intelligent people to land their admissions in uni, and land their roles at their companies. They would be wrong to name hard work as the key differentiator first and foremost, and thankfully they don't. You minmax your odds by taking as much luck and opportunity as you can get and combining that with as much smart work and hard work as you can. And even then, you will usually lose out to someone who was even smarter, harder working, luckier, or more than one of the above. For example, that top 5 or top 10 admission could easily have been a top 3, etc. That consulting, finance, and asset management career could've been in IB. That big pharma career could have been a medical or dental career with a clear pathway to starting a business.
There are plenty of people in the world with these kinds of success stories, but it's rare for people to openly acknowledge their own luck instead of chalking it all up to their own work ethic. Not surprising given how self-gratifying it is to underappreciate luck and overappreciate one's own ethical superiority. Survivorship bias is a fucking massive blindspot, and it's clear to me that you suffer from not understanding or appreciating what that is.