Because he taught Kakas endurance.
Because he is the fourth generation Huo Ying of Konoha Village.
Because he is the father of the protagonist Naruto.
Because Watergate sealed Kyubi no Youko's strength on Naruto and asked him to protect the village.
Please don't dwell on Watergate. Watergate is just a legend.
His name is Namikaze Minato, the fourth generation of Huo Ying.