Why Has Game of Thrones Sidelined Tyrion?
"It’s the latest in a line of blunders. My colleague Chris Orr listed them in his Season 8 preview: “Tyrion hasn’t had a good idea in seasons now (truce with the slaver cities? sneak attack on Casterly Rock? let’s go snatch a zombie?).” Each of these wasn’t a mere dicey gamble whose upsides were mixed with downsides. They each backfired terribly, with consequences for his new queen, Daenerys, and the cause of liberation and world-saving she’s thought to represent. She’s lost soldiers, cities, and a dragon on his account.
He, in turn, has lost not only his cunning, but also his place within the show’s hierarchy of characters. In the first few seasons, Tyrion could nearly be thought of as the protagonist. "
read article by Spencer Kornhaber
A 'Game of Thrones' Mystery: What Happened to Tyrion? - The Atlantic