Kehas was counted first because they carried the Aron, which contained the Torah. One must give proper honor to the Torah and those who learn it. This answer raises another question. The Keli Yakar explains that this was done to show that the crown of Torah is free for all to take. If it were given to the bechor, he might think that he received it because he was older.
Age has nothing to do with Torah.
Those crowns are inherited, yet the crown of Torah is free for all to take. Honoring Torah and those who learn it is very important. We must stand up for our Rebbeim, and speak with them in a most respectful way. We must listen to what they say, and follow their halachic rulings. That great honor that is given to Talmidei Chachomim can be ours.