The demigods are not in competition with Krishna but are in a progression to him
God by definition is the Supreme Being. And there can be only one Supreme. Yet the Bhagavad-gita talks about multiple worshipable beings, devatas.
Who are these beings?
Some people equate them with the “false gods” condemned in certain religions as God’s competitors.
But the Gita is clear that the devatas are real beings. They occupy in the cosmic administration the posts of departmental heads under the Supreme Being, Krishna. As they have some of the powers of God, Gita commentators often refer to them as demigods.
Through the demigods, Krishna facilitates the progress of people who are not spiritually evolved enough to worship him. By arranging for his subordinates, the demigods, to act as his surrogates, intermediate objects of worship, he provides people the facility to worship according to their mentalities.
When people choose to worship one of the demigods, Krishna with extraordinary large-heartedness strengthens their faith in that demigod (07.21) and also empowers the demigods to bestow benedictions on their worshipers ( 07.22). But these demigods are not eternal. Of course, as souls, they are eternal, but as occupiers of the posts of cosmic administrators, their tenure and power is temporary. So they cannot grant the eternal liberation that the eternal Supreme Being can grant (07.23). To gain that perennial benediction, demigod worshipers need to grow in spiritual understanding and graduate to the worship of the Supreme Being. Till then, the system of demigod worship accommodates within the precincts of dharma those not yet ready to fulfill the purpose of dharma: love for the Supreme.
Of course, for those enterprising enough to embrace that purpose, the Gita’s conclusion (18.66) recommends single-minded devotion to Krishna, thereby facilitating their swift progress towards life’s supreme attainment – eternal life of love in the spiritual world.