2003 was Montoya’s one big chance. IIRC, with two races to go, Schumi was on 82 points and Juan was on 79.
However, his disastrous race in the USA GP ended his title hopes for all. The DNF when leading in Japan was just beating the dead horse (and Williams losing the WCC of course).
Obviously, Montoya did retire twice in 03 from the lead, due no fault of his own. Austria and Japan were 20 easy points lost. Sadly that did cost him the WDC at the end.