In my opinion, i think their government just controlling the investors not to invest too much on crypto. They were afraid for investors not to invest for the benefits of their government.
Investing? Airdrop is not a kind of investing but a way to earn free crypto currencies with out really doing nothing, well not really all of them since most of them need you to do something for them.
I don't know the reason of them banning the airdrop but I think with a lot of people in their country spamming the media or the internet with those sharing links to the projects is getting out of their control.