سَيِّدُ الْقَوْمِ فِي السَّفَرِ خَادِمُهُمْ can be understood from two complementary angles.
First: a designated leader should attend to companions' welfare, comfort, and difficulties. Service is part of leadership.
Second: someone who genuinely serves the group deserves honor for that service, even without holding formal authority.
Example: a younger traveler arranges water and luggage for the group. The service is valuable, but this act does not automatically appoint the traveler as everyone's official leader. Honor through service and formal responsibility are distinct matters.