Other than hoarding gold (edit: or cryptos, or anything similar), what is the best way to make sure my net worth doesn't just go to zero from one day to the next?
Assuming you are a regular person, and that you do not have the US Government out to get you, put your money in an FDIC (or equivalent) insured bank account. The financial system is pretty good at making sure that even with these hacks and breaches, the actual depositors don't actually lose money. Other alternatives such as hoarding gold, digging a hole in your backyard and burying cash, buying cryptocurrencies has a higher chance of resulting in your losing your money than if you just put it in a bank account.
You should diversify. Have some money in a 401k, and an IRA or brokerage account invested in a whole market fund mostly, with a smaller amount in bonds. Buy a house.
All of those except for the house can be stolen in one shot from your bank, unless you spread your accounts among multiple banks, and that increases your risk of accidentally losing one of them.
