why were the wargs in the hobbit so much more intelligent than the wargs in the lord of the rings

The Wargs of The Hobbit might have seemed more intelligent because Tolkien wrote it as a children's book and might have been more self-indulgent then he was when he wrote The Lord of the Rings. The Hobbit was more of a fairy story--or, at least, what Tolkien thought a fairy story ought to be.

EDIT: Also, the wolves that attacked the Fellowship in Eregion might have been of a different nature than the Wargs that were encountered near Goblin-town. The bodies of the wolves slain by the Fellowship were gone the following morning, suggesting that they were not typical Wargs. Werewolves maybe?