If you have a bone to pick, it is with the executor of the estate who failed to make it clear to you when you were given the money in 9/2016 that this would be taxable income to you on your 2016 tax return. Whenever one receives an unexpected windfall, it's prudent to understand whether it is income that is taxable to you and then to determine if you must adjust your regular tax withholding or make an estimated tax payment to avoid an underpayment penalty. It's just the way the US tax system works. See IRS Tax Topic 306: https://www.irs.gov/taxtopics/tc306.html
Making less in 2016 that in 2015 may have actually decreased your underpayment penalty since one of the safe harbors depends on your previous year's tax liability.
