Last year they had the ROG Phone (9 I think? Not sure) and the Zenfone 12 Ultra (basically non gamer version of ROG Phone but mostly unremarkable. The year before was the 11 Ultra, and year before that the 10, which was a sort of okay 5.8" phone with pretty bad software support, but they killed the small phone thing in favour of an Ultra model, kind of like how Apple did with their Mini to the Plus model. Interestingly, the Plus model has been killed in favour of a flatter model with worse basically everything. The Air then had poor sales, because people don't like a worse phone for more money, so I wonder what's next for Apple?).
Terrible software support (as Asus does), unremarkable hardware, and not having any killer features, gimmicks, or similar meant poor sales. I guess now they don't want to lose more money?