Here's why:
* Adverbial phrases modify verbs, adjectives, or other adverbs. They tell us how, when, where, or to what extent something is done.
* Compound adjectives are two or more words that function as a single adjective describing a noun.
In the case of "extremely bewildered," the phrase acts as a single adjective describing a person or their state. For example:
* The extremely bewildered tourist looked around in confusion.
Here, "extremely bewildered" modifies the noun "tourist," telling us about their state of mind. It does not modify a verb, adjective, or adverb.