Yashamaru actually hated Rasa for using Karura as a tool and sealing a monster in her unborn child, which ultimately led to her death.
Here’s a concise, insightful post explaining Yashamaru’s complex feelings toward Gaara: why did yashamaru hate gaara
To understand why Yashamaru hated Gaara, one must look beyond a simple summary of events. It was not a singular cause, but a complex storm of grief, psychological manipulation, and a desperate lack of choice. Yashamaru actually hated Rasa for using Karura as
Years later, during the Fourth Shinobi World War, the Fourth Kazekage, Rasa , was reanimated and finally revealed the truth to Gaara. but a complex storm of grief