Saudi and Chinese govt don't have anything to hide. They both make it clear to their public about who they are and the public supports them. Saudis are no different than their govt (unlike us Iranians who are completely diff from our govt) and the Chinese govt has the support of its people. The Chinese govt has implemented reform after reform for more than 3 decades. Today they have social freedom and their economy has been growing at an insane speed for 3+ decades. They do have censorship, but for different reaons than in Iran.
In Iran NO GROUP supports the mullahs, not one. The young people hate them, women hate them, the religous people hate them, the secularists hate them, the nationalists hate them etc... Everything they also say to the public is a lie, everything. Their lies are also so big that they need to hide the truth at all costs. The Chinese govt doesn't go around claiming to its people that palis are innocent creatures who are being ripped apart by the zionists etc... IR does. If people has access to info they would see how "innocent" the palis are, how much they hate Iranians, how strong wahabism is in pali land etc... The people would see how the people around the world are living and how Iranians outside Iran are living and then they would look at their own lives. The people would see how the world has moved on and how globalization has brought people from around the world closer together and how nobody is interested in conflict etc... They would see how much Iran could grow economically, socially and politically if the country opened up. They would see how every single thing that IR says is bs. They would see how Israeli people are closer to Iranians than arabs are. They would see facebook groups like "Israel loves Iran" etc...
Of course many people already use VPN to access the net, but the slow speeds limit what people can do. The net is off limits for the older generation Iranians who don't have time to go to forums and talk to people. With fast internet they could go on different websites using VPN and read the truth.