White hats wouldn't have helped here. There was no code bug; it was simply an issue of having too few validators.
Although this is true that white hats wouldn't have helped since it's not code bug and 1/1 DVN is apparently intended mechanism that is even the LayerZero themselves said they are against it. But still, there is turmoil about how severely underpaid white hats are after disclosing bug that could potentially put hundred million dollar at risk and only getting $3k for that. Honestly there were critics about 1/1 DVN setup by wormhole co founder before rsETH exploit happened.
If these aren't fixed, those hackers will keep doing the same exact thing you mentioned. Though yeah, the 1/1 DVN is problem on the KelpDAO themselves not a code problem.