Sansa Trevellan: As a circle mage she was used to having things decided for her. She never had strong opinions about being in a circle and saw the pros/cons. When brought to the inquisition she enjoyed the change and knew the import regarding its success. She figured she'd continue with the Inquisition until it felt time to end it. While not a bad person, she was nobility and made questionable decisions using the inquisition's influence. Ex: Making Servis a smuggler.
"Corypheus must be stopped."
Demona Addar: Coming from a mercenary group, her moral code was rather loose. When power was practically handed to her she just went with it. She accepted being the Herald of Andraste as well as Inquisitor without any fuss even though she didn't even believe in the Maker. She happily accepted the role with no plans to end the inquisition anytime soon even with Corypheus dead.
"I'll do it for my own power."
Nirvana Lavellan: All she wanted was to return to the forests with her clan, yet couldn't ignore the breach/Corypheus. She didn't want to be Inquisitor but had to do it. She refused to let the power corrupt her and stuck to a strong set of ideals; seeing how easily the inquisition could lose its way with some of its people already corrupt (Leliana). Once it was over and with Solas abandoning her she wanted to simply to get away from the inquisition, its politics (Viviene for example was the only companion she didn't like until learning of Blackwall's lie), the shemlen (even though being treated better than practically every elf ever), and return to her old life where she belonged.
"I'll do it because it's right."