a driver who is universally regarded as the best driver in F1
I think he may well be the best driver in F1, But F1 is a team sport and I don't think he's the best team player. I certainly believe he started in McLaren being reasonably open and helpful to Lewis, but whether it was the support Lewis got off the track or the ability/lack of respect he showed on it, Alonso was switched off. I don't think he was ever the "mentor" type of No.1 driver, and I don't think he'll ever be happy having no team orders on or off the track.
I'm sure Alonso has learned from his mistakes of 2007
Agreed, but I'm not sure that they wouldn't return under pressure. This is what killed his 2007 championship because he took the rivalry onto the track and his driving style/ability was compromised. Since then he hasn't been threatened in the same way. Problem is, I believe part of Alonso's brilliance is his determination to shine, and that's in his team aswell as the WDC. This determination prevents him ever swithching off, keeps him open to new tactical ideas (hmm) and keeps his brain able to calculate during a race. Unfortunately, when opportunity has offered itself, he has shown no real signs of desiring to be part of the WCC at the potential expense of the WDC.
Here's the crux, if I had to put values to it I would say Alonso is 90% WDC, 10% WCC. Ferrari, on the other hand are probably 60% WCC and 40% WDC.
So why the move by Ferrari?
From The Telegraph 12th September 2008
Ferrari's announcement that Raikkonen would be staying until the end of 2010, alongside Felipe Massa, ended months of speculation that double champion Fernando Alonso would move to the Italian team when the Finn's contract expired at the end of next season.
Between the lines (my style), Todt was after Alonso, everyone knew Alonso would be the No.1 driver, but in 2008 Massa started to really compete and was vying for at least equal standing. The new guy in charge, Domenicali was concerned about whether Alonso really had moved on from 2007, so extended Kimi as contract one year as security to keep Kimi locked in and focused for 2009 and give Massa the opportunity for the No.1 spot.
July 2009, Massa gets injured, and as veravista says:
Ferrari are resigned to not having him
Because they cannot be out of contention for the WCC two years running and keep their budget I think the hand of Jean Todt as CEO advised Domenicali to take advantage of the budget and accrue Kimi's costs into this year, push Alonso's costs down due to the market and other well known events, and lock in Alonso.
Let's not forget that both Renault's recent WCCs and Alonso's WDCs have been with Fisichella as the No.2 driver, so If Ferrari have written off Massa for a season or more they may think that they have bought the 2005/6 winning drivers solution.