Imagine the world's various nations are like big boats floating along the ocean. The ship's captains demand total silence on deck, they concentrate on where they're going and its everyone else's job to support them by agreeing the current course is the only realistic choice.
Then one of the boat's captains invents a mad idea called "free speech" where people are allowed to criticise his choices. All the other captains are horrified, from their point of view this was a dangerous choice, it could result in mutiny.
Oddly, over time, a number of other ships try this "free speech" idea out. Why would any of them even entertain such an idea?
In short, it's because it took only a small period for boats with "free speech" to gain massive advantages over the others. They began to spot their mistakes and correct them. This led to a massive upsurge in scientific development enabling them to build things like factories where they produced guns, tanks, bombs and so forth. Their boats became bigger, better and, more importantly, were able to change direction so became very hard to predict.
After years of progressing in exactly the same direction year after year boats were suddenly starting to improve themselves.
Why should free speech walk hand in hand with scientific progress?
We'll keep it simple and explain using the story of the flat earth vs round earth theories.
In the past the captains all knew the earth was flat because it looked flat and the maps they used told them it was. So, the evidence of their own eyes, combined with knowledge which went back thousands of generations and had never failed them. It was obvious, the earth is flat and they were very skilled at navigating its edges.
On the other hand, if anyone took the heretical and obviously wrong idea that the earth was round seriously, everyone would die when they sailed over the edge. The thought itself needed to be supressed for the good of everyone and so anyone who spoke in that direction was killed as a heritic.
The only place you could survive if you considered this obviously wrong idea was on a ship which was trying out "free speech". Over time one of those ships started to get a little braver and sail closer to the supposed 'edge of the earth'. Debate onboard had reached fever pitch and many of the inhabitants had begun to accept the earth was in fact round. The eventual tactical advantages to this ship led them to "confirm" this truth: the world is round.
So far this piece is predictable. Lets now add a twist.
Imagine the first boat to discover the earth was round also suffered a major trauma, a world war with another ship which was convinced the world was flat. In the aftermath the idea of a flat earth became taboo, in the same way it had previously been to suggest the world was round. Being a "flatist" got associated with being against everything the people on the boat stood for, including "free speech". To be accused of advocating "flatism" became a terrible thing in itself and those who did were shunned and ignored.
Over time the captains of the ship realised such name calling was a great way to supress any possible rivals and would often accuse people of being a "flatist" simply to avoid a debate. They had not really enjoyed the "free speech" period and many of them were happy to have a way of shutting people up again.
Also, such debates were pointless because the captains all knew the earth is round and were very skilled in navigating its edges. They knew this because the maps they used went back generations and had not failed. If anyone took the heretical idea that the earth was flat seriously everyone would die so, the thought itself needed to be supressed, and for years anyone who dared speak in that direction had to be killed as a heritic.
The "free speech" idea of old got dropped and forgotten about by the captains. It was mainly trivialised into a debate about how rude a popular onboard comedian could be or whether or not it was ok to have the ship's stripper on deck during the day. Trivial matters were ok but anything serious had to be approved by the captain for everyone else's safety.
Flat earth theory was not discussed at all after that, no one dared. This protected it from criticism and ironically stored up the possible threat of it making a return as people who were not familiar with the debate announced to themselves how alike to a flat surfact the ocean was. This horrified many on the boat, it was proved how seductive a theory flatism was and justified it being legally supressed. Free speech was officially abolished onboard many of the boats, the stakes were far too high, the captains knew their directions nowadays anyway. What the ship's captains needed was total silence on deck so they could concentrate on where they were going. It was everyone else's job to support them by agreeing their current course was the only realistic choice.