For me, it was a combination of things, but mostly just working and socking away as much as I could, in both tax deferred and after-tax investments. I did have some help from family, though. For instance, after a bad divorce in 1996, I moved in with my Grandmom, and rented out my condo. Early in my career I tended to work a second job, but in 1996 when it was getting bad, I started delivering pizzas in the evenings, and that brought in some pretty good money. Sometimes I'd actually take home more from the delivery job than the main job. However, the main job paid for my insurance, 401k, etc, so that's not entirely a fair comparison.
In late 2003, I moved into the house across the street from Grandmom, that had been in the family since before the Civil War. Well, the property at least. The house had been built in 1916, and Grandmom and Granddad inherited it in the 1960s. Grandmom had been using it as a rental, but as she got older, and the house too, it was getting to be a hassle. So, she put my name on the title, as well as my uncle, so that he didn't get screwed out of his ultimate inheritance.
Getting the house basically for free allowed me to take the proceeds from the condo and invest them. I also took out an HELOC on the house, and some of that went into investments. When Grandmom passed away in 2015, I think I got about $60,000. Plus the house went from 1/3 mine, 1/3 hers, and 1/3 my uncle's, to 50/50 me/uncle. The $60K was nice, but at that point I was over $1M in invested assets, so it wasn't life changing. Being able to live in the house rent free, and take out that HELOC and invest, plus investing the proceeds from the condo were a bigger game changer. So, I put this under "help from family," although I guess others might call it "getting my inheritance early".
Now, my paternal Granddad, and then Dad, died within 6 months of each other. What I got from that was pretty substantial. And, I guess you could say it was life changing. The HELOC had converted to a 10 year fixed mortgage, starting in early 2015. I had been paying it down somewhat aggressively, but once the inheritance cleared, I had it paid in full, around Jan/Feb of 2018. I also used a good chunk of it as the down payment on my current house, and having the old place mortgage free, I was able to keep both properties, and take my time clearing the old house out.
I finally sold the old house October of last year. The check they cut me, for my portion of the proceeds, was something like $157K. It did trigger a bit of a tax bill, but it wasn't too horrible because I was able to write some stuff off against it, and take some strategic stock losses. So, maybe $140-150K is what I cleared, after taxes. A nice boost, but at that point I had about $2M in invested assets, so it didn't seem like it changed my life in an earth shattering way. Actually, not having to deal with the house anymore, plus the carrying costs (taxes, insurance, minimum utilities) cutting the grass, worrying about it getting broken into/squatters, etc was a bigger peace-of-mind than getting that check at settlement.
If Grandmom hadn't let me move into the house back in 2003, I'm sure I would have moved into something of a step-up house. Perhaps a modest single-family home, with a 2-car garage. And, if I'd never gotten any inheritance from her, nor my Grandad and Dad, I'd still be doing fairly well now. But, my life would definitely have taken a different course. I'm pretty sure I wouldn't be in the house I am, currently, at least. I might have moved from my theoretical step-up house to something a bit nicer, but it probably wouldn't be a nice as what I have now.
So I guess I'd put the factors of my wealth accumulation, in order of importance:
1) saving/investing from working for the man/megacorp.
2) family help
3) inheritance.
Edit: 4) almost forgot: taking in housemates. That has definitely helped to some degree, over the years. Moreso in the early years, but even now, the income is a nice bonus.