The import of the words mugdha iva is that although Kṛṣṇa knows everything, here He pretended that He did not understand why the demon had entered among the calves, and He informed Baladeva by a sign.
He (Krsna) very slowly approached the demon (in the form of a calf), as if He did not understand the demon's intentions - SB 10.11.42
Expressions researched:
"Then He very slowly approached the demon, as if He did not understand the demon's intentions"
Srimad-Bhagavatam
SB Canto 10.1 to 10.13
When the Supreme Personality of Godhead saw that the demon had assumed the form of a calf and entered among the groups of other calves, He pointed out to Baladeva, "Here is another demon." Then He very slowly approached the demon, as if He did not understand the demon's intentions.
When the Supreme Personality of Godhead saw that the demon had assumed the form of a calf and entered among the groups of other calves, He pointed out to Baladeva, "Here is another demon." Then He very slowly approached the demon, as if He did not understand the demon's intentions.