Complex sentence: After the tenth verse, Bhattatiri realised that the boy was the Lord himself, and understood that Poonthanam's bhakti was more pleasing to the Lord than his own superior knowledge of Vibhakti (Sanskrit grammar) and learning.
Split into simpler sentences: After the tenth verse Bhattatiri realised that the boy was the Lord himself. He now understood that Poonthanam's bhakti was more pleasing to the Lord than his Vibhakti (Sanskrit grammar) and learning.