If I were to say a couple reasons why the XFL might be a success this time, and where the AAF wasn't, are:
• Vince McMahon - He has a lot more money now than he did when he tried the XFL years ago, and he's willing to sink in over a half billion dollars of his own money to get the league going. He's a very savvy businessman, and arguably the best promoter or marketer in the world. He's also smart enough to hire Oliver Luck, and mostly stay out of the way, it looks like entirely out of the way when it comes to actual operations and running the league.
• It will be on both TV, and the internet. The previous time around McMahon/WWE couldn't charge, and had to essentially pay NBC to broadcast the games (as did the AAF) years ago. This time they aren't doing that. Some of the games will be on Fox, some on ABC/ESPN, FS1, and there remains the option of WWE's own channel, and all will be available on the net, crafted to where revenue will go back to the XFL (and McMahon).
• The pay for players will be better, and they will have more name players than the AAF. This allows the league to lure players like Landry Jones to play for them saying "would you rather be stuck in back-up limbo, or play in the XFL for a little less money, and a chance to be a star?"
• They have better coaches than the AAF could afford. In fact, quite a few of the coaches could, maybe should, be coaching in the NFL. Also deeper pockets in the league mean better coaching and support staff across the board.
• At first I thought the city locations were a mistake, now I think they are smart. Going to big markets increases chances of revenue. Yes, a few games could be in nasty winter weather, but enough fans, and players won't mind, compared to the market sizes.
• There was nothing wrong with the play in the AAF, other than it lacked stars, specifically at QB. The rules were good, and the pace of the game good. The XFL will have similar rules, move quick, and has better players.