1. We desperately need some kind of jolt to get everyone interested in this team again. At least it'll give us something to talk about.
2. Paul Allen has the money to make it happen. More importantly Jackson needs a different challenge, instead of taking a team already pretty good to the next level he can completely build a team from near scratch. Remember Jackson has never coached a championship team where his team didn't already have arguably the league's best player (Kobe, Shaq, Jordan). Even though he has more rings he will never be considered Red Auerbach's equal unless he talkes a bad team and takes it to the promised land.
3. We hate him. He probably thinks we're beneath him. So what? It's almost too audacious not to try! This is the guy who smokes peyote or and talks in zen and Buddhism and all that. In other words the guy is unconventional. What's more unconventional than going to a (to the national media) a city you dissed?
TV Tropes even has a perfect description of this.
This would be a epic plot twist of Shakespearean proportions and I think that would fit Jackson's sensibility.
4. We may not be the biggest city or fan base but I have no doubt that a NBA championship would mean more to the the Blazers and the fans than any other franchise. I definitely think that's a worthwhile challenge. Win with Lebron, celebrate in Miami so what? You're forgotten in five years. As much as Boston crows about what a great sports town they are they've had like a zillion teams win titles there.
With Portland it would be earth shattering, like aliens invading earth. There would be no equivalent. There can be no greater challenge than that.
5. Despite Paul's negative experience with giving Holmgren too much power as GM/coach I'm sure he'd be willing to give Jackson a blank check and carte blanche power to do whatever he wants. As highly respected as Holmgren is Jackson makes him look like Mike Tice, the coach with the most NBA championships in history. Even the Vulcans would back off when dealing with a authority like Jackson.
6. Blazers need some swagger. Of course it could very well end up like Larry Brown with the Knicks, but this franchise desperately needs someone as arrogant like Jackson. There's such a dark cloud and sadness with what happened with Oden and Roy and the season. We need this guy to start giving fans confidence, taking shot at our rivals, giving us an identity different from "oh those poor Blazers" and so on.
7. Revenge. All else fails at least we'll get some poetic justice on Phil Jackson. If he's a complete flop at least he'll have been forced to spend time in the city and the weather he so infamously insulted. Hey I like rain buddy. I like the Beavers too.
8. Disrespect. All the NBA teams have shown tepid interest despite the fact that the coach who has won the most NBA titles is a free agent. If Portland shows strong interest why not? Knick make MIKE WOODSON as their coach rather than court Jackson, wouldn't he be ticked off? Why not go to Portland and work his zen magic here and show the rest of the NBA how foolish they were not to hire him? I mean if Belichick quit the Patriots and then wanted to come back 4 years later how many NFL teams do you think would fire their existing HC outright to hire Belichick?