Mood

There is a lot of games out there which have a great mood.
What makes the mood?

I guess a few things:
1. graphics
2. music / sound fx
3. story and characters
4. gameplay
5. visual FX

Probably might be more to the list.
But a mix of these creates the mood.

As the two previous elements (a story & a character) are something solid, catchable,
this element is more emotional. Related to feelings.
It involves and requires player's sensibilty.

Why to search for it in a hyper-casual games?

Same as before.
To bring emotions.
To make the fun a bit deeper.
To leave a memory.