It seems to me that Honda put a huge effort into this year's car (at the cost of doing very little development on last year's), and when they had a winner they sold the team to Brawn at a huge discount.
This means they got NO benefit for all their hard work as Brawn is not even using Honda power.
Certainly flatters Button, but he is not such a hot driver in my view: the car makes more difference. As evidence consider how often we see a "Noahs Ark" grid, with the cars lined up 2x2 or nearly so.
At least he stuck around long enough to get rewarded for his loyalty, remember Villeneuve was with BAR for their "wilderness years" but ended up regarded as a loser. Luck of the business, I suppose.
Red Bull has been very strong this year, too, I wonder how much has to do with their wind tunnel and how much to do with the talent of the drivers.