Pariksit Maharaja was surprised that Vrtrasura, whose purpose was to give trouble and anxiety to others, was one of these devotees, even on a battlefield. What was the reason for Vrtrasura's advancement

Expressions researched:
"Parīkṣit Mahārāja was surprised that Vṛtrāsura, whose purpose was to give trouble and anxiety to others, was one of these devotees, even on a battlefield. What was the reason for Vṛtrāsura's advancement"

Srimad-Bhagavatam

SB Canto 6

Therefore Parīkṣit Mahārāja was surprised that Vṛtrāsura, whose purpose was to give trouble and anxiety to others, was one of these devotees, even on a battlefield. What was the reason for Vṛtrāsura's advancement?.

SB 6.14.6, Translation and Purport

Vṛtrāsura was situated in the blazing fire of battle and was an infamous, sinful demon, always engaged in giving troubles and anxieties to others. How could such a demon become so greatly Kṛṣṇa conscious?

It has been described that a nārāyaṇa-parāyaṇa, a pure devotee, is rarely found even among millions and millions of persons. Therefore Parīkṣit Mahārāja was surprised that Vṛtrāsura, whose purpose was to give trouble and anxiety to others, was one of these devotees, even on a battlefield. What was the reason for Vṛtrāsura's advancement?