That portion of the paper is weak. In the body of the article they say that (unspecifed, as far as I can tell) genetic factors "cannot be ruled out" and then go on to list other culprits for the dramatic increase in T2D, especially in the past two decades.
Some of these are: A sedentary lifestyle. Obesity including in children. Political instability in some countries, leading to poor care. A culture of women not taking physical activity. The focus of the "uncontrolled rise" in the rate of T2D is the Gulf countries (members of the Gulf Cooperation Council, i.e. basically Arabian Peninsula nations). It points to data showing that the prevalence of T2D in Saudi Arabia is 25.4 percent as of 2014 (!).
They don't talk much, or at all, about diet. From my experience living in, and traveling to, countries in the area, the diet in many of these countries has been high in refined sugar for a long time. Since the middle of the last century, soda-type drinks (often originally implanted by Coke or Pepsi franchises) have become ubiquitous. Those drinks, and highly sweetened coffee and tea, are a common social ice-breaker (replacing alcohol, in the Gulf countries that ban or restrict booze). Sweet drinks are, in some countries, also part of the desert Bedouin heritage. Health-care ranges from pretty good in some countries to primitive in others. There is a widespread culture of hospitality and it is just "not done" to refuse food when profferred. This is lovely, of course. (All of this paragraph is just my own first-hand observation.)
The paper says that T2D is now the fifth-leading cause of death in the Arab world. The countries of the region are trying to do something about it, in the form of the "Riyadh Declaration" promoting a healthy lifestyle. (But to my mind it would be a huge challenge to get effective regional action on the issue.)
It also says that a lot of information is simply unavailable at this point and urges that the issue be studied further.
It would be interesting to get
@hichamgsm's perspective on the matter, albeit from the extreme western end of the Arab world. ("Maghreb" means "west" in Arabic.)