Lots of pundits have posited that Trump could actually beat Clinton in New York. Most of them make a variant of two arguments: One, his appeal to white working class voters is strong; two: he’s more of a rough-and-tumble, born-and-bred New Yorker than she is, and has a stronger claim to the state. Both of these arguments are trivially true.
Furthermore, the New York primary was closed — no independents allowed — and because Democrats outnumber Republicans in New York state by a two-to-one margin, Hillary’s big vote total was exactly what one would expect her to get if she had the same level of organic support among Democrats as Trump did among Republicans.
There’s another caveat: Trump ran against two other candidates; Clinton ran against only one. That further dilutes the strength of her victory.
And another: Polls show that the independent voters who couldn’t vote because of New York’s primary rules would have supported either Trump or Bernie Sanders; very few would have chosen Clinton.