This is important to remember. One reason it might feel unfair now though is some combination of a) to many people, it is clear the war was a mistake and they remember always being against it now and b) some 35% of the current adult US population, including myself, wasn’t old enough to be polled then, but was legitimately against the war always.
I'm not sure anything would have changed if we knew we were lied to. 2001-2002 was a strange time. A lot of people just wanted war--with anyone. It didn't really matter who we invaded. The Cold War ending meant the USA was out of overt enemies, and this was a real bummer to people who loved war and belligerence, so the sooner we could make enemies and start fighting, the better.
No they were not.
https://news.gallup.com/poll/8038/seventytwo-percent-america...
Iraq was a popular war.