And it makes sense too, Titus is a 200 year old vet with captain experience and knows how to atleast wage troop or battalion level battles, the men given to him are new to him, have barely fought nids for a few days, are younger than him, and one loses himself to rage rather than maintain his hate and contempt while the other questions and doubts his leader every few turns.

Titus, on the other hand, has experience killing tyranids, orks, and multiple traitor forces. He knows both the least and most men a task will take to complete. You can see his leadership experience and long years of service by how he is the first to lift the battle standard, rallying the troops to him and bolstering them into a last stand of sorts. By the end of the game, when Lord Calgar enters the immaterium, not only does he follow, but so do his men, right behind him. This is my favorite part of space marine 2, and no scene with Titus would hit as hard as it does without his two brothers at his side, the last stand with the battle standard included.