The study shows that a simulation where randomness plays a major role can produce similar wealth distribution to what's observed in the world. But that doesn't rule out a more deterministic mechanism.
If I walk into my kitchen and see a broken egg on the floor, it could have been left by a wayward chicken. But the simpler explanation is that my spouse broke an egg from the refrigerator. If I prove that my spouse was home and up before me this morning, I don't really need to disprove the chicken theory to reasonably believe the simpler explanation.