The article states it comes from real-estate. That implies some amount of buying and selling. Unless they just happened to have a single 5M mansion sitting around.
Speaking as a millennial, you don't just "get into real estate", usually it's seeded by a large amount of generational wealth/inheritance.
Someone struggling to put a deposit together for their own home isn't going to make bank out of flipping houses and contributing to the shit housing sector. It really is true that all it takes to make money is money, it's almost effortless.