economic slowdown
With the economy slowing and inflation rising Americans are turning to wholesalers etailers and discounters. It's been noted that people are also avoiding driving to stores and purchasing online to avoid rising fuel costs in addition to sales tax.
Right or wrong with regard to not paying sales tax on mail or online purchased goods, in the end what makes and breaks Amazon are their low prices and razor thin margins. NYS sales tax will make them less competitive with regard to other etailers: for example right now they may have similar prices with newegg on computer gear, but post sales tax they may not.
NY is a pretty huge market and I am sure Amazon doesn't want to get pushed out of it through the "Amzaon Tax." Especially just as the economic contraction and inflation make the prospect of purchasing from online etailers more attractive than ever before.