Totalitarian dictatorships were largely the product of the Bolshevik Revolution of 1917. The imperative of attaining and maintaining absolute control over a large population spread out over a very large expanse of territory while indoctrinating that population in an alien ideology required total control over the population. Not only were the physical movements of that population to be completely controlled, but the thought processes were to be shaped according to Marxist-Leninist dogma. Deviations from official thinking were penalized by imprisonment under the harshest conditions, and by death.
Implementation of totalitarianism was heavily dependent upon the control of information within and across borders. Before the introduction of radio, newspapers and word of mouth were the principal means of communicating across borders. Restrained by the means of transportation at the time -- mostly trains -- the ability of "subversive" elements to spread malicious information that could weaken state control of the population was extremely limited.
As the technologies of communications evolved, the ability of governments to limit what their populations read, heard or saw became more limited.
The Chinese Communist Party attempted for decades to strictly control the flow of information within China's borders. It still does attempt to maintain tight controls, but its ability to both control the population while facilitating economic growth has, not unexpectedly, proven problematic. The Chinese government does place strict limits on the abilities of internet service providers to operate within its country, but over time the technologies of communication have opened large swathes of China to increasing flows of information.
The only true totalitarian regime in existence today, China's continued efforts at controlling the flow of information for the purpose of ensuring the continued political dominance of the Communist Party aside, is North Korea. More than any other country, North Korea has succeeded in maintaing very tight controls on information. Its geography -- a peninsula with China to the north and its adversary, South Korea, to the south -- is highly conducive to the restrictions on the flow of information maintained by the North Korean regime. Its physical isolation combined with its brutal human rights practices have enabled it to impose a totalitarian system unlike any other. Some information does penetrate North Korea's borders from the outside world, but it is limited.
In conclusion, the evolution of communications technologies has played a vital role in the inability of governments to impose total control over the populations in the manner once practiced by the Soviet Union, China, and still practiced today in North Korea.