For example Azeris, Turkmens, Tajiks transitioning from the Arabic script, and Buryats from the Mongol script.
And why wasn’t there a cyrillisation of Georgian and Armenian?
To me the script changes seemed unnecessary, but I’m curious what you think
Arabic only has three vowels (each can be long or short) but the Turkic languages have many more vowels so the Arabic script couldn’t represent the vowels properly. The Mongolian script also has issues with silent letters and spells words like how they sounded several centuries ago. The USSR also changed the spelling of Russian words and removed some letters from the Russian alphabet so words would be spelled how they sound.
Turkic languages that use/used the Arabic script extended it with additional letters and diacritics.
That’s true and that’s the reason why Turkic people had low literacy rate. Arabic has 3 vowels and modern Turkish has 8. Back in late days it has too much effort to learn but now language itself literally got rid of its own unique sounds to fit in to Latin alphabet.