Lord Viṣṇu Himself, the Supreme Personality of Godhead, is the reservoir of all pleasure. Therefore, what benefit would He derive from siding with the demigods? What interest would He fulfill in this way? Since the Lord is transcendental, why should He fear the asuras, and how could He be envious of them?
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
न ह्यस्यार्थः सुरगणैः साक्षान्निःश्रेयसात्मनः । नैवासुरेभ्यो विद्वेषो नोद्वेगश्चागुणस्य हि
na hyasyārthaḥ suragaṇaiḥ sākṣānniḥśreyasātmanaḥ | naivāsurebhyo vidveṣo nodvegaścāguṇasya hi
SB 7.1.2