Kuwait supported Iraq during the Iran Iraq war, Kuwait did not want Iran's fundamentalism spreading any more than the US did
The support Kuwait gave Iraq was in the form of finacial backing, after the war Kuwait back out of this support of Iraq leaving Iraq in heavy debt
At the same time Iraq accused Kuwait of drilling under the boarder into Iraq'a oil fields, accusations that have not been disproved.
On this basis Iraq invaded Kuwait and the US and full knowledge prior to the invasion and promised Iraq they would stay out of it and saw it solely as a boarder dispute that was not their concern
Once the invasions happened though the Saudis become nervous over Iraq's actions fearing they maybe dragged into the dispute and called on the US to get involved.