Question about the swing vote

Alright so! Watching every season I still don't get how anybody gets to this position!
At first I thought it was luck but I reevaluated after watching Kass's both runs (Cagayan and Cambodia) and Sarah's Game Changers game as both of these players (more of Kass than Sarah) really mastered this strategy and I think it's honestly one of the best strategies ever!

I don't get however how they were always stuck in this position? Am I wrong, this being luck, or is it really a good well executed strategy on their part and if so help me understand how they pulled it off