Could someone tell me why is よう being used in this sentence?


From the context I think he meant: Why was that person so scared?

But what does this よう mean? Couldn't it be just 怯え?

> あの怯え **よう** は何だ？




This kind of よう after masu-stem forms a noun phrase meaning "the way of ～",
"how one ～", "one's manner of ～", etc. I think it's a relatively uncommon,
literary usage.

> あの怯えようは何だ？  
>  (lit.) What's his way of being frightened? / Hey look how he's frightened!

よう may appear in the following forms:

  * `dictionary-form + 様【よう】`: so that; in order to (泳ぐよう, 見るよう, 食べるよう) Usu. in kana
  * `masu-stem + 様【よう】`: way of ～ (泳ぎよう, 見よう, 食べよう) Usu. in kana
  * As part of the volitional-form of vowel-stem verbs: Let's ～ ; I think I will ～ (見よう, 食べよう)
  * `dictionary-form + 用【よう】`: for the purpose of ～ (泳ぐ用, 見る用, 食べる用)

Examples:

>   * 見ようによっては、正しいと言える。  
>  Depending on how you see it, you can say it's correct.
>   * 馬鹿とはさみは使いよう (Japanese proverb)  
>  (lit.) As for idiots and scissors, it's all about how you use them.  
>  Everything comes in handy when used right.
>

`masu-stem + っぷり` is a similar pattern which emphasizes "how
{extraordinary/intensively/etc} one does something". (See
[this](https://japanese.stackexchange.com/q/13390/5010))

  * あの怯えっぷりは何だ？ ≒ あの怯えようは何だ？
  * 彼の飲みっぷりは素晴らしい。 I'm impressed that he's a good drinker.

怯え in its own right means "fear" (noun), which is not something one can
directly see. So you need よう/っぷり/かた after 怯え.




This kind of よう after masu-stem forms a noun phrase meaning "the way of ～",
"how one ～", "one's manner of ～", etc. I think it's a relatively uncommon,
literary usage.

> あの怯えようは何だ？  
>  (lit.) What's his way of being frightened? / Hey look how he's frightened!

よう may appear in the following forms:

  * `dictionary-form + 様【よう】`: so that; in order to (泳ぐよう, 見るよう, 食べるよう) Usu. in kana
  * `masu-stem + 様【よう】`: way of ～ (泳ぎよう, 見よう, 食べよう) Usu. in kana
  * As part of the volitional-form of vowel-stem verbs: Let's ～ ; I think I will ～ (見よう, 食べよう)
  * `dictionary-form + 用【よう】`: for the purpose of ～ (泳ぐ用, 見る用, 食べる用)

Examples:

>   * 見ようによっては、正しいと言える。  
>  Depending on how you see it, you can say it's correct.
>   * 馬鹿とはさみは使いよう (Japanese proverb)  
>  (lit.) As for idiots and scissors, it's all about how you use them.  
>  Everything comes in handy when used right.
>

`masu-stem + っぷり` is a similar pattern which emphasizes "how
{extraordinary/intensively/etc} one does something". (See
[this](https://japanese.stackexchange.com/q/13390/5010))

  * あの怯えっぷりは何だ？ ≒ あの怯えようは何だ？
  * 彼の飲みっぷりは素晴らしい。 I'm impressed that he's a good drinker.

怯え in its own right means "fear" (noun), which is not something one can
directly see. So you need よう/っぷり/かた after 怯え.

