What does 是 mean/indicate in sentences such as 虽然有些人吃素是因为宗教的关系，但小林不一样?

Question

I'm a beginner in Chinese and I'd like to ask you something about these sentences below :

虽然有些人吃素是因为宗教的关系，但小林不一样。

and

...小林不太喜欢吃肉食，是因为有些肉食有很多骨头，让他麻烦死了。

What does 是 in those sentences mean/indicate? I've tried to look for the explanation of why 是 is placed before 因为 but I couldn't find anything except this structure : "之所以...是因为". But still, I don't think that the "之所以...是因为" structure is the one being used here.

The others are :

有些肉食是没有骨头的。

and

在印尼，很多种菜是要直接用他自己的手指吃的。

For this one, I'm quite sure 是…的 here is that one 是…的 structure which is used to emphasize (like time, place, or manner). But the thing is, I don't know whether or not the 是…的 structure can be used to emphasize something like 没有 or 要.

Could you please explain to me? Thank you in advance.

Answer 1

「是」因爲 translates to 「is」because of or 「is」due to. There's an implicit phrase that's omitted in these sentences, which is (the reason behind)...「is」due to....

雖然有些人吃素「是」因爲宗教的關係，但小林不一樣。

Even though (the reasons behind) some people eating vegetarian「is」due to religious considerations, 小林 is different.

小林不太喜歡吃肉食，「是」因爲有些肉食有很多骨頭，讓他麻煩死了。

(The reason for) 小林 disliking meat「is」because some meaty foods contain a lot of bones which greatly inconveniences him.

Like the English equivalent of these sentences, the phrase the reason behind is omitted. The English equivalent, however, will also omit「is」for grammatical reasons:

Even though some people eat vegetarian due to religious considerations, 小林 is different. 小林 dislikes meat because some meaty foods contain a lot of bones which greatly inconveniences him.

---

Please note that in Chinese, the omission of the reason behind is necessary in this case; we don't say ...的原因是因爲..., especially in written materials, as this is highly redundant.

Answer 2

是 is used for "emphasis; stress; emphasize" (my English is poor; I don't know which one is correct).

You can say:

虽然有些人吃素因为宗教的关系

but in this sentence if you add 是, then you can hear more emphasis (强调), and it sounds more natural (自然), and sounds better (好听).

Weird? Because 好听? Yes, why we use those special word 是因为好听? 100%