Why does Season 7 have less episodes?

Related questions

1. Is Season 7 the last season for Game of Thrones?
2. Are Jon Snow and Daenerys siblings or cousins?
3. Who created the Night Walkers?
4. Who is the king of seven kingdoms?
5. How many episodes are in season 7 of Game of Thrones?
6. Who Wrote Season 7?
7. How did Rhaegal die?
8. Who sits on Iron Throne in the end?

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2. #producers
3. #series
4. #danger
5. #seven
6. #benioff
7. #going
8. #season
9. #there
10. #delay
11. #david
12. #creative
13. #executive
14. #episodes
15. #because
16. #thrones