How did Charles de Gaulle become the leading figure of French liberation movement? While acknowledging his talents and the personality, I find it hard to believe that he was the only or the most likely person to take this place.
Status in the military
De Gaulle was neither particularly highly ranked nor particularly well-known in the military. Indeed, he showed himself well in the beginning of the war, and was made an acting general (au titre provisoire) - the appointment that was never made permanent due to his later split with the official power. He didn't have much to show in terms of past achievements, unlike the people who were considered WW1 heros (Philippe Pétain among them). Neither was he among the commanding French officers evacuated at Dunkirk, as by then he had joined the government.
Political status
At the moment of the armstice de Gaulle was a former cabinet member of sub-ministerial rank. Unlike other political figures hosted at that time in London, de Gaulle didn't represent a government in exile or anything like that. Moreover, the allies continued treating Vichy government as the official one for several years after.
Affiliation with Pétain
Although at the time of the armstice de Gaulle advocated continuing war (if necessary) in colonies, and thus at odds with Marchal Pétain, he was known to be long-term protégé of the Marchal and owed the latter many of his promotions. A rather poisonous association it seems.
Alliance with Stalin
De Gaulles' detractors, notably the descendants of general Giraud, make much of de Gaulles' cooperation with Stalin, whose support was rather costly: giving the Communists the leading role in the French resistance and later inviting them to his government (including some army deserters from 1940). However, to get such a support de Gaulle would have to be by 1941 the head of the French resistance, so the question remains.
Resistance vs. the army
Finally, after the allied landing in Africa and the French army re-entering the fight, it is not clear why de Gaulle would be given preference over the other army chiefs, notably Giraud.
Algiers putch of 1961 might have also shown that former combat generals didn't necessarily held high respect for de Gaulle.
In other words, while the man's talents were unquestionable, I see neither a gradual rise to power, nor being the right man in the right place at the right time, nor a preferred choice of Stalin and Churchill.
To suggest more specific questions :
Suggested criteria
I think the following were necessary for de Gaulle to become what he became:
Hypothesis
From what I gathered in the French media: de Gaulle was one of few outgoing government members favouring continuation of the war, and he had the audacity to flee to Britain on the last day of the validity of his diplomatic credentials (before the new government took office). Churchill authorized de Gaulle's famous broadcast in a hope to attract some bigger figure, but no one showed up (so he was stuck with de Gaulle, though the two didn't really liked each other).
This hypothesis addresses the last of my bullets above, and the some extent the one before the last. It is still unclear what credibility de Gaulle had with the French, and why Churchill looked for a civilian rather than a military leader. It also gives impression that de Gaulle was Churchill's creation - a view that many would probably object.