Why did they switch actors in Game of Thrones?

Related questions

1. Why did Game of Thrones replace Daario?
2. Did Stannis Baratheon actor change?
3. Is Bran Stark the same actor?
4. Did they recast the mountain in Game of Thrones?
5. Is Bran the 3 eyed raven?
6. Why did Littlefinger betray Ned Stark?
7. Did the actor playing Jaime Lannister change?
8. Did they change Daario in Game of Thrones?
9. Why did Gregor clegane actor change?
10. Why did they change actors for Daario?

Tags

1. #refused
2. #leave
3. #because
4. #character
5. #therefore
6. #naharis
7. #ended
8. #transporter
9. #scenes
10. #replaced
11. #portray
12. #would
13. #refueled
14. #opportunity
15. #original
16. #daario
17. #previous
18. #skrein
19. #chose
20. #actor