Srimad-Bhagavatam: Canto 6 - Chapter 1 - Verse 8
लोका: सपाला यस्येमे श्वसन्ति विवशा वशे ।द्विजा इव शिचा बद्धा: स काल इह कारणम् ॥ ८ ॥
lokāḥ sapālā yasyemeśvasanti vivaśā vaśedvijā iva śicā baddhāḥsa kāla iha kāraṇam
All living beings in all the planets of this universe, including the presiding deities of all the planets, are fully under the control of the Lord. They work like birds caught in a net, who cannot move independently.
The difference between the suras and the asuras is that the suras know that nothing can happen without the desire of the Supreme Personality of Godhead, whereas the asuras cannot understand the supreme will of the Lord. In this fight, Vṛtrāsura is actually the sura, whereas Indra is the asura. No one can act independently; rather, everyone acts under the direction of the Supreme Personality of Godhead. Therefore victory and defeat come according to the results of one’s karma, and the judgment is given by the Supreme Lord (karmaṇā-daiva-netreṇa). Since we act under the control of the Supreme according to our karma, no one is independent, from Brahmā down to the insignificant ant. Whether we are defeated or victorious, the Supreme Lord is always victorious because everyone acts under His directions.