I wouldn’t say that necessarily makes Button the worst driver to be a champion. When he won the title in 2009, he’d spent two years driving cars that were so uncompetitive he might as well have been towing a caravan at every race. He showed a lot of promise in 2004, when he was the highest-placed non-Ferrari driver at the end of the season, and again in 2006 when he scored more points than anyone else in the second half of the season.
I also think Button takes a lot of criticism for the second half of 2009. A lot of people think he simply coasted to the title after his last win in Turkey, but Brawn actually ran out of money. They brought an upgrade for the BGP-001 to Silverstone that didn’t work, and then spent the rest of their development budget trying to fix it. By the time the final flyaway leg came around, they were relying on race-by-race sponsorship deals with Ricahrd Branson and local sponsors just to make it to the next round of the championsihp. The fact that Button managed to hold on long enough to win the title is a testament to his skill – and it’s even more impressive when you consider that the chassis he was driving when he won the title in Brazil had taken part in every single test, practice session, qualifying session and race from the first test in Barcelona. Most teams build about eight cars over the course of the season. Brawn only had enough money for three: one for Button, one for Barrichello, and a spare (that Barrichello used in Singapore after crashing in qualifying, so if Button crashed in any of the next three races, his championship was literally over because he would not be able to race).
Yes, Button has gotten better since he moved to McLaren. And yes, the Button of 2010-2012 would probably beat the Button of 2009 in the Brawn. But that doesn’t make him any less of a driver. By rights, Brawn GP should not have made it to Melbourne in 2009. The fact that Button won the championship with them against all the odds, development blunders and monetary problems means that his title should be remembered as one of the greatest achievements in sport.
As for who I think would be the worst champion, I would actually say Lewis Hamilton. Don’t get me wrong; I think he’ll go down as one of the sport’s all-time greats. But when he won the title in 2008, he had never driven a bad car in Formula 1 (when everyone who had won a title else had driven a bad car), and as exciting as the 2008 Brazilian Grand Prix was, Hamilton’s title was decided by Timo Glock’s pit strategy. If Toyota had gotten it right, Hamilton wouldn’t have been champion at all. He made up for it in 2009 when McLaren built a bad car and he rallied the team onwards, with the end result being a late-season resurgence that saw him take two wins, and thereby demonstrating that he really was a deserving champion, but at the time, I felt Hamilton hadn’t really worked for his title and kind of lucked into it at the last corner in Brazil.