It clearly states the gaining of followers, mods to the leadership score, & the stacking of follower counts.
What it does not address is if the Crusader ability grants a cohort (as Leadership does). The description of the ability says to treat Crusader as the leadership feat. Just a niggling question but trying to head off any questions about it from players down the road.
Your prowess and ability draw countless followers to your banner. You gain followers as if you had the Leadership feat. In addition, you add your tier to your leadership score when determining the number of followers you gain. Whenever you are within 100 feet of such followers, each follower can use the surge ability once per day without needing to expend mythic power. The followers use the same die type as your surge ability. If you have or gain the Leadership feat, you gain followers from both this ability and the Leadership feat (in effect doubling the number of followers gained).
This feat enables you to attract a loyal cohort and a number of devoted subordinates who assist you. A cohort is generally an NPC with class levels, while followers are typically lower level NPCs. See Table: Leadership for what level of cohort and how many followers you can recruit.
Since Crusader does not specifically call out that it grants you a cohort, I do not think it gives you one. It references followers, which is a specific benefit of Leadership separate from the cohort that feat also grants, so that's the only thing it affects.