Learn Icelandic: Ég sé strætóinn af því að hann er stór.

In Icelandic, af því að is the standard way to say 'because.' It literally translates to 'of it that.' Even though it is three words, you should treat it as a single connecting unit.

What happens to the word order after af því að?

The word order after af því að stays exactly like a normal, independent sentence: subject (hann), then verb (er), then adjective (stór). This is called affirmative main-clause word order, and it is the standard pattern used after af því að when the statement is positive.

Why does the sentence use hann (he) for a bus instead of það (it)?

In Icelandic, pronouns must match the grammatical gender of the noun they refer to. The word for bus, strætó, is a masculine noun. Therefore, you must use the masculine pronoun hann to say 'it' when talking about the bus.

Is strætóinn in the accusative case here because of the verb að sjá (to see)?

Yes! The verb sjá (here as ég sé) requires the thing you see to be in the accusative case. The base word strætó does not change its spelling in the accusative, so we just add the masculine accusative definite article -inn to mean 'the bus'.