Learn French: Est-ce qu'il fallait beaucoup d'argent pour devenir riche ? - Did one need a lot of money to become rich?

Il fallait is the imparfait (past tense) of the impersonal expression il faut (it is necessary / one needs). We use the imparfait here because it describes a continuous past state or a general condition, rather than a single completed action. It translates to "was it necessary" or "did one need".

Who does the il refer to in il fallait?

Nobody! Just like in the English phrase "it is raining", the il in il fallait does not refer to a specific person. It is an impersonal pronoun. To express "did one need" or "did people need" in a general sense, French uses this impersonal structure.

Why is it beaucoup d'argent and not beaucoup de l'argent?

After expressions of quantity like beaucoup (a lot), you must use de (or d' before a vowel) without the definite article (le, la, l', les). Since argent starts with a vowel, de drops its 'e' and becomes d'.

Why do we use pour before devenir?

In French, when you want to express "in order to" do something, you use pour followed by the infinitive form of the verb. Here, pour devenir translates to "in order to become" or simply "to become".