Switching to Proof of Stake created a host of new problems, in this case “the list of upcoming block proposers is public and it is possible to map their IP addresses. This means that attackers could identify which validators are due to propose a block and target them with a denial-of-service (DOS) attack that leaves them unable to propose their block in time. This could create opportunities for an attacker to profit.”

Hubris coming back to bite them.