They didn’t ignore his mother, they argued that she hadn’t been in the US for enough time. For a birth abroad with one citizen parent, between December 24, 1952 and November 13, 1986, the U.S. citizen parent must have been physically present in the United States or one of its outlying possessions for 10 years prior to the person’s birth, at least five of which were after the age of 14. After 1986 it became 5 years / 2 years after 14.

She was 18 when she gave birth to Barack. He was born in Hawaii so it didn’t matter.

At one point some people tried to argue John McCain wasnt eligible either as he was born in the Panama Canal Zone, which was made no difference.