I honestly don't know where you guys are taught this kind of false history?
3 of the 4 founders of the current Sunni schools of fiqh were Arabs originally from Arabia.
https://en.wikipedia.org/wiki/Malik_ibn_Anas
https://en.wikipedia.org/wiki/Al-Shafi‘i
https://en.wikipedia.org/wiki/Ahmad_ibn_Hanbal
The fourth, Abu Hanifa, was born in modern-day Iraq (Arab land and ruled by Arabs), spoke Arabic as his mother tongue, was Arabized, had an Arabic name and studied under Arabs. Besides his ancestry is not known with certainty but his paternal lineage is believed to have been from Afghanistan originally. Not Iran.
The hadith collections already existed and were completed and recorded by Arab scholars. They were only collected into larger works by those individuals that you have mentioned who again were Arabized, wrote in Arabic and were from Afghanistan and not Iran.
Arabic grammar? Are you joking? Arabic grammar was already well-defined long before Islam emerged and Semitic languages which Arabic is a key part of, have the oldest fixed grammar of all languages in the world and alphabets.
As for this news. What a surprise.
Domestic Iranian militants, just like those that have killed 50.000 Iranians since 1979 (MKO and various separatists belonging to various ethnic groups) are just doing what they are doing on a monthly basis. KSA must be an incredibly powerful country since it is behind every single attack in the world! Quite amazing in fact.