...Which was created under centuries-old influence of the Brotherhood, to start with. It wasn't "natural process", it was influenced. Again, cheating. Now, let's took the situation into nationalism era - when "new additions" to Charis would start to recall that they were independent nations before Charisian conquest, and realize, that Charisian were able to conquer them only by cheating...
By the point that becomes common knowledge or is even known outside the IC the IC would have won straight up, the church would be dead and the lie revealed to the world. At that point it doesn't really matter at all and those nations would still be loyal to Charis because of the political situation and how they like being a part of the charisian empire and all that that entails.
Correction: he didn't want to help them. He could easily repeat his "seijin" trick, for example, or create some sort of "seer" persona, or other tricks to gain influence on other countries.
He just didn't want to, because of goalpost moving: instead of encouraging the whole planet toward innovative mindset, he just used the whole planet as a giant human shield for Charis.
I mean again you don't seem to understand that Merlin is a human who is at this point loyal to Charis and would not work against the interest of Charis if at all possible. Plus I mean so far the expansion of Charisian technology and the spread of it's inventions have entirely accomplished the goal of making the rest of the world embrace an innovative mindset to as great an extent as the society they live in allows. As in Sidermark, Dohlar, The Temple Lands, United Provinces, Earl Rainbow Waters area and probably a fair few border states have entirely embraced innovation and making new technology which is probably over 70% of the world's population. Desnair and Harchong have also become innovative as well to keep up but to a lesser extent as they cannot become more innovative without their society collapsing and their internal regime is too strongly in place to be toppled but even they are innovating and their society is likely to fall apart fairly soon at which point 100% of Safeholds population would have fully embraced innovation. At the end of TFT 75% of the worlds population is full steam ahead innovating and the remainder is innovating as well but to a lesser extent. Effectively Merlin and the IC have entirely achieved their goal of creating an innovative mindset across the entire planet.