My understanding is that the imperfect tense in French is used for past habits and ongoing events. Examples:
- Je jouais au tennis tous les mercredis (past habit)
- Je regardais la télévision lorsque quelqu'un a frappé à la porte. (past ongoing event)
However, I have heard the following dialogue in the TV series Marseille:
- Mayor: C'est pour ça que tu as voté contre la vente du J1?
- Barrès: Il fallait bien ouvrir les hostilités.
- Mayor: Tu l'as fait trop tôt. Un mois de plus et Marseille tombait dans ta main.
Context: The mayor of Marseille and his deputy Lucas Barrès are arguing about why the latter has turned against the former.
In the last sentence, the verb "tomber" does not refer neither to a past habit, nor to an ongoing past event, but rather to a past conditional event which would happen if Barrès had acted differently. Therefore, shouldn't the conditional tense be used instead of the imperfect tense ?