"Danzō could utilise multiple nature transformations which included Wind, Earth, Water, and Fire Release, as well as Yin and Yang Release.[2] He was particularly proficient in Wind Release, exhaling powerful vacuum-based attacks that could either slash like blades or pierce like bullets."

Quote from Naruto Wiki.

My theory for why he is fire here- there was need for Kage-class ninja with Fire-Lightning barrier- and he actualy c*e all of the styles- and they also didn't want this version of him to be too op- so he doesn't have all of releases included in type of his attacks damage.

That's how I see it

for me it's okay but about mfune it's another thing to me xD

he look like he are a lightning user but he are a earth user and i want him to be lightning even if he aren't that ninja who can release lightning justu

That's what i think too, in addition to that, maybe Shisui's Sharing*so somehow affects Danzo's nature to be a Fire-Ninja, since Shisui is a Fire-Ninja and Danzo's main skill in the game is from Shisui's Sharingan ..

Sharingan has nothing to do with Chakra Nature.

Sasuke is good example. But he forced to master Fire to exceed his father's expectation.

For Danzo's case, it was probably his fighting style is suited better to use Wind to win over Sasuke's lighting.

He'd use fire jutsus if he has to.

Rather than sharingan, fire nature users are common in the Uchiha clan. Sasuke is shown to be using variations of Chidori a lot more than fire jutsu (pre-amaterasu), which is why he can be seen as a lightning user. As for Danzo, since he has shisui's eye, Tencent probably needed a ninja for the fire-lightning barrier (fire-wind-lightning when skill broken - just like shisui).

As for OP, danzo's affinity as fire makes sense compared to other ninjas where they don't have any nature chakras. For example, why are shikamaru and his dad are earth nature just like someone like shino, ino or enma? In the end, it doesn't matter in the game.

Everyone knows Fire is common for Uchiha. What I meant is Sharingan still has nothing to do with Chakra Nature.

Sharingan is merely an extra tool to a ninja.

Sasuke learnt Chidori from Kakashi, because he knew Sasuke was lightning affinity. That's why i said Sasuke is good example.

Each character grew and during their own phases; they always used the most powerful techniques. That goes with Danzo, where he rather used Wind to fight.