To simplify the matter to what financially makes sense:
For the same property, walking away and buying it again at $230k means a $150k gain when the home appreciates back to the original purchase price, a 65% gain versus 0% for staying put. It doesn’t even include the delta from monthly payment difference.
It just seems to make sense to walk away.
Ethically, as long as the banks are taking money from the government, one should have no qualm in taking advantage of the situation. Of course it depends on how you feel about it.