Is なんだろう in fact 何だろう in the sentence?


I was trying to understand a fragment from [My Clueless First
Friend](https://www.youtube.com/watch?v=c5BiGTjdbFw&t=1375s), and got stuck
with this sentence:

> ごめん ね 多分 私 の こと を からかいたかった だけ な ん だろう けど 巻き込んで 嫌 な 気持ち に させちゃって

In the subtitles it's translated this way:

> Oh, I'm sorry about that... I'm sure they were trying to tease me, but you
> got dragged into this too because of me...

I used different tools (jisho.org, rikaichamp, ichi.moe) and sources of
information (subs, auto subs)... The results differ slightly...

The thing I'm the least certain about is なんだろう. The tools say it's 3 or even 4
words. But I guess it's after all 2 words: 何だろう. And it's probably like adding
"I guess" to a sentence, expresses uncertainty. Or maybe she's just being
humble, polite, doesn't want to sound abrupt.




This なん is **not** a contraction of なに (何). Forget 何 for now. Here, なん is a
contraction of なの, where this ん/の is something known as explanatory-の.

  * [What is the meaning of ～んです/～のだ/etc?](https://japanese.stackexchange.com/q/5398/5010)
  * Wasabi: [Explanatory のだ （んだ）](https://www.wasabi-jpn.com/japanese-grammar/explanatory-noda/)

You can understand this sentence ending as follows:

  * 私のことをからかいたかった。  
They wanted to tease me.

  * 私のことをからかいたかった **だけだ** 。  
They **just** wanted to tease me.

  * 私のことをからかいたかっただけ **なんだ** 。  
**It's that** they just wanted to tease me.

  * 私のことをからかいたかっただけなん **だろう** 。  
It's **perhaps** that they just wanted to tease me.

  * 私のことをからかいたかっただけなんだろう **けど** 、...  
It's perhaps that they just wanted to tease me, **but**...




This なん is **not** a contraction of なに (何). Forget 何 for now. Here, なん is a
contraction of なの, where this ん/の is something known as explanatory-の.

  * [What is the meaning of ～んです/～のだ/etc?](https://japanese.stackexchange.com/q/5398/5010)
  * Wasabi: [Explanatory のだ （んだ）](https://www.wasabi-jpn.com/japanese-grammar/explanatory-noda/)

You can understand this sentence ending as follows:

  * 私のことをからかいたかった。  
They wanted to tease me.

  * 私のことをからかいたかった **だけだ** 。  
They **just** wanted to tease me.

  * 私のことをからかいたかっただけ **なんだ** 。  
**It's that** they just wanted to tease me.

  * 私のことをからかいたかっただけなん **だろう** 。  
It's **perhaps** that they just wanted to tease me.

  * 私のことをからかいたかっただけなんだろう **けど** 、...  
It's perhaps that they just wanted to tease me, **but**...

