And yet a lot of the time (especially early to mid 2003(?)) Ralf Schumacher was quicker than him. Does not compute.
Ralf beat Juan in the championship when they were team-mates just the once. That would be Montoya's first F1 season. After that, Ralf never really had the measure of him again except on the odd occasion. And after his US GP smash in '04 his career was pretty much done. Juan could have had many more years in F1 at that stage, but made the mistake of going to McLaren.
By the way, 2003 wouldn't be the example you were looking for. That year, he made the podium 8 times in a row in the middle of the season
But anyway, I wouldn't place much emphasis on his Champ Car and Indy 500 wins, CART was on it's last legs and the Indy 500 was a joke by then.
Montoya won the Champ Car title in '99. It wasn't until 2000 that the series started to slide a bit, and 2001 saw the real turning point (the cancelled race at Texas being the catalyst). The Penske and Ganassi teams became full-time Indy Racing League teams for 2001, Andretti not long after that.
As for the Indy 500 being a joke - really not sure about that. It had been an IRL-only event since the CART/IRL break-up in 1996, and 2000 was the first time that Tony George had managed to get a CART team to show up to the race. The fact that this CART team - Ganassi - turned up and dominated the race (Montoya led 167 of 200 laps IIRC) says more about the quality of Ganassi's preparation than it does about the quality of the event.
I've always felt Montoya was overrated, his reputation mainly being there due to one overtaking move in Brazil 2001. There are too many excuses for his many bad races he had in F1.
He had some appalling reliability to contend with in his time in F1. Take 2001 - he retired 11 times that year, and 7 of those were down to the car breaking IIRC (and of the remainder, at least once he was taken out by someone else - Verstappen in Brazil).
He still holds a few records in F1 I believe - fastest lap ever recorded in a Formula 1 car (pre-qualifying for the '04 Italian GP, average speed of over 162mph), and he still holds the lap record at the Turkish GP circuit. I don't see how his talent or speed could be questioned. His temperament, absolutely
And maybe he was a bit hard on the car (though as I pointed out abpve the Williams FW23 was hardly a paragon of reliability, and the McLarens that he drove weren't bullet-proof either).
He came along at a time when the Ferrari-Schumacher juggernaut was getting into its stride, and by the time that ended he found himself in a McLaren team built around Kimi up against The Daddy™ in a Renault team that was doing a better job than everyone else. So he buggered off to go have fun again in NASCAR. Can't say that I blame him.