It's because the foundation was already there. The dad is a top official in the royal court. The mother is a genius in finance and had sense to keep the account of the father's spending on hand as proof. The son is a social genius just not good at studying sincerely. All of them were good people who were pushed too far.

I think there are a lot of rebirth novels where rather than creating a full-on pre-rebirth character and coming up with ways to develop that character pre- and post rebirth the author just creates a complete, has everything they need to succeed post-rebirth character and the pre-rebirth version is exactly the same only very dumb. That's why Ning Yanting and Jiang Yunlan both had things (a successful political career, a bunch of lucrative businesses and a ledger of how much Ning Yanting spends on family) that they probably shouldn't have had pre-rebirth.

Just because you have all to succeed doesn't keep you from making foolish décisions. I have a real life exemple of people I know who had their life laid out for them by there parents. They had 80 acres of land, a fully équiped farm and a house all already paid and they still managed to bankrupt themselves. When you have to take a loan to have you're farm and not even 20 acres of land and hear this you just want to beat them up and ask just what thé hell their brains are for.