More important than a nationality of the hackers (to me at least) is the personality of the payer for services. It’s clearly mentioned in the article:

Solomon and Azima allege that Dechert undertook the hack-and-leak operation in the interest of its client, Sheikh Saud bin Saqr al-Qasimi, ruler of the Middle Eastern emirate of Ras Al Khaimah.

What kind of gun was used in a killing is much less important than who paid for the killing, no?