When Thomas offered his group leader position to Ainsworth, none of the survivors within his group showed any resistance.
After all, for them, it didn't matter who was the leader as long as they were capable. Thomas merely did his best in leading the group, and he didn't treat any members badly, so they weren't against him being the leader.
However, they witnessed Ainsworth and his team eliminate a horde of zombies, so when compared to Thomas, they preferred that Ainsworth become their group leader. After all, Ainsworth and his team's power was more than enough to guarantee their safety.
Furthermore, they also had a very good impression of Ainsworth due to his charm and charisma. Those with great looks would naturally yield a good first impression, especially when they were capable and showed good will to those who were inferior to them.
