Twitter wins again. We keep reducing these complex multivariate social issues to simple cause-effect situations then beating one another up over what the simple cause is. When we're doing definitions, the key phrase is "necessary and sufficient" In this case, being rich or poor is neither necessary nor sufficient since we have plenty of examples of things working out with either of these two things being missing. So…
You are totally missing the point Matthew Prince is trying to make, that is, you need to have a "safety net" before you can take risks. If one can't even get them fed and not worrying about what the next meal is and where to stay, all bets are off.
If you don't agree with me, name one entrepreneur who has found a startup that exited successfully(IPO or Acquisition) by now and that the founder(s) were living below poverty line or on social welfare. Borrowing money from parents doesn't count as living below poverty does it? Having parents or friends or family to lean onto economically means there is a safety net there.