During the time Linthia spent as a captain, Rex has never seen her be this serious.
Out of the three captains, she was the most timid—the little sister who can't quite reach the appropriate level. She tried, even the people knew that she tried but she was simply unfit to reach the appropriate level.
It was not because she didn't have the talent.
Rex makes sure to equalize their playing ground from the very start so it's not that.
Instead, Linthia was held back because of her lackluster flames of ego.
She only wanted to be good enough as a captain, the constant insecurity—from seeing how Dindora and Gelmar rose in power snuffed out what little ego she had. Even if there was still an ember inside, it was incomparable to the others.
It was precisely why she couldn't evoke an evolution in her bloodline despite Rex's help.
Gelmar wanted to be strong enough to protect his son and make him happy.