Learn Swedish: Innan han flyttade hade han pendlat till jobbet. - Before he moved, he had commuted to work.

This is because of the V2 (verb-second) rule. The entire first clause, Innan han flyttade (Before he moved), counts as the first building block of the sentence. To keep the main verb in the second position, the verb hade must come right after it, swapping places with the subject han.

Why do we use two different past tenses (flyttade and hade pendlat) in the same sentence?

Just like in English, the past perfect tense (hade pendlat, meaning "had commuted") is used to talk about something that happened before another event in the past. He was commuting first, and then he moved (flyttade).

Why does Swedish use the definite form jobbet (the job) instead of just saying till jobb (to work)?

In English you usually say "I commute to work", but in Swedish it is most natural to use the definite form jobbet when referring to your workplace. It's similar to how an English speaker might say "going to the office".

If I flip the sentence around and put "He had commuted to work" first, how does the word order change?