Jeremy Lin is not short.
Only in basketball is Lin considered short. There he is, a "small" 6'3" guy dribbling through a forest of seven-footers, looking for just a sliver of sunlight, fighting the same battle that an average Asian man or woman might fight in a crowded Manhattan subway car.
Yao, indeed, occupied the penthouse of the tower, blessed with height and athleticism and pedigree that make Lin seem like a busboy.
Ultimately though, Yao was too inaccessible, too superhuman for an Asian kid's dreams. What Asian kid dreams of being 7'6", especially when your dad is 5'6"?
But 6'3"? Just possible.
In fact, both Lin's parents are 5'6".
Somewhere, little Asian kids are praying for a growth spurt.
Somewhere, a white or black or brown kid is thinking of getting a "17" shirt.
Somewhere, Wilt Chamberlain sighs.
 A couple other reasons: Of course, Lin is more accessible to Asian-Americans because he's American. Jay Caspian Kang alludes to this. He's also more accessible to other Asians, because truthfully, some Asians are less receptive of the Chinese (as opposed to the Taiwanese), for various social and political reasons.
 The Houston Rockets picked Yao with the first overall pick of the 2002 NBA Draft, and they expected him to become an impact player. There was, however, a particularly memorable doubter. That draft year turned out to be fairly weak, with only Amare Stoudemire, Caron Butler, Tayshaun Prince, Carlos Boozer, and Luis Scola rating as semi-impact or better players.