I would ask you for youre opinion why footy is so popular than now. I created a map like footy ( read the opinions of my map on http://www.wc3sear.ch/index.php?p=Maps&ID=8277 ) and I want to make it popular because its funny to play it and have some very interesting things which hasn't footy yet.
Footman Frenzy is one of the worst maps i've ever played. I got no problem with dota but footman really pisses me off. I cant explain why it is that popular
I never liked any footmen map because it seem to have no balance and no strategies. It seem that the only way is sent troop in and make sure you get enough money then you domain over everyone. I'll give it a try because you say it has AI.
That's probly my next map project to offer different strategy to win the game if someone else is domaining in footmen game... after when I'm done with my VS Maul map, I'm experiencing difficult to balance tower cost and effective to reflect the levels creep's health and bounty.
You're actually asking the question "Why are some maps popular?" Gods know, no-one else does. Figure out why some maps are popular and others aren't and we'll all thank you for it.
Probably hosting, if a map's hosted at lot, it'll keep getting hosted.