Hussein was left in power intentionally. He was a business parter of the Bush family, but then he threatened to quit accepting US dollars for oil, and he also overpumped (undercutting alleged OPEC's 'control' of oil prices). So Bush entrapped Hussein.

Iraq had always claimed the oil fields in Northern Kuwait, and Bush Sr. signaled (through U.S. ambassador to Iraq, April Glaspie), that if Iraq invaded Kuwait, the U.S. would view it as an 'inter-Arab affair' and would take no action. That was on the news networks the day the meeting between Hussein and Glaspie met. Then Hussein invaded Kuwait, and Bush said "This will not stand."

All on the record.