I HATE this “I’m well off because I work hard” attitude. Plenty of people work fucking hard in minimum wage jobs and still struggle to make ends meet.
No one has said that people in NMW jobs DON'T work hard, the OP asked how those who are well off had made their money, so people are giving honest answers - yes some were lucky and married into or were born into money but not everyone 
People are well off because they’re lucky - either lucky to have a skill/talent that, when they harness it, can make them lots of money or lucky because of circumstances.
That's a very narrow minded view of the world. Yes, some people are lucky and possibly haven't had to work hard for their money.
But I'm not lucky, nor was I born into or married into money (most of my family still live on the same council estate largely living off the state).
I worked fucking hard all my life starting in school, it's the biggest reason I've never done a NMW job and now own my own company.
I worked my arse off to get good grades while my friends were messing about thinking it didn't matter.
I got a full time job at 18 and studied around it to get qualified in my chosen field, while my friends spent the next 4 years at uni getting pissed, partying and racking up debt.
I spent 15 years honing and developing my skills, getting good at what I do, building up a network to get myself in a position to start my own company and get clients based on the reputation I'd built for myself.
But to do this I spent the time from my DS was 3 until he was 8 working away from home and doing 60, 70, 80 hour weeks.
Any of that sound like I was lucky and didn't have to work hard?