PURPORT

Since, sage Kardama was a brahmana and Svayambhuva was a ksatriya, the sage was not supposed to offer obeisances to the King because socially his position was greater than the King's. But he offered his obeisances to Svayambhuva Manu because as Manu, King and Emperor, he was the representative of the Supreme Lord. The Supreme Lord is always worshipable, regardless of whether one is a brahmana, a ksatriya or a sudra. As the representative of the Supreme Lord, the King deserved respectful obeisances from everyone.