You're forgetting one key element: Cartoon Network. GW is the first gundam series aired on Cartoon Network. Up until then, anime was mostly a subculture over here. You had your choice of crappy-dub Sailor Moon (the original is actually pretty good), Ronin Warriors (which is still one of my favorites), or Pokemon. Well, Fox did play Escaflowne, but they didn't do a good job of the dub and it didn't go over well. I don't consider Power Rangers in this catagory. >< Then CN comes along, gets ahold of GW, and pimp the living hell out of it. They put it on right after school, so a lot of kids can rush home and watch. And an instant fangirl-base was born.
Personal, I love GW. The story is a lot deeper than people realize, but then, I've also read all the manga for it. That does help. (yes, Strider, pacifisim is a dream, but Relena is increadibly naieve). And yeah, you have to watch the whole thing. I didn't get it all when I first watched it. Most of what I got the first time I saw it was pretty characters and explosions. A lot of the political stuff went over my head. I've watched it several times since then, read essays and manga and discussed it a lot, and I enjoy it more now than I did. I'm not saying it's for everyone, and I'm not saying it's the best anime around, but there's a lot more to the series than it looks when you first see it.