Ignored? No, most of that administration actively encouraged and fostered Hamas for years and years. To their mind, it was better for their aims to build Hamas into a hardline organization, and more appealing than the alternative, which was a Palestine which was (slowly) becoming more open to compromise, more diplomatic (around the end of Arafat).

It pushed their nationalist agenda further to have a boogeyman in the form of Hamas, than to have to answer awkward questions like "Palestine is being very reasonable and open, so why isn't Israel?"