Learn Spanish (Latin America): El campesino no usaba el tractor por la tormenta. - The farmer did not use the tractor because of the storm.

You use por before a noun to express the cause or reason for something ("because of the storm"). If you want to use porque ("because"), you have to follow it with a full clause that includes a conjugated verb, like porque había una tormenta (because there was a storm).

Why is the verb usaba in the imperfect tense instead of the preterite (usó)?

The imperfect usaba implies an ongoing situation in the past ("wasn't using it") or a habitual action during a period of bad weather. If the speaker had used the preterite (no usó), it would frame the action as a single, definitively completed event ("he didn't use it on that one specific occasion").

Is there a difference between a campesino and a granjero?

Yes, although both are often translated as "farmer." A granjero typically owns or manages a commercial farm (granja). Campesino is a broader term for someone who lives and works in the countryside (el campo), often referring to a rural laborer, peasant, or field worker who might not own the land they work.

How does the por in this sentence relate to concessive phrases like por más que?