“And they will not stop fighting you, until they turn you back from your Religion; if they are able.” [Surah al- Baqarah 2:217]
So typically this was the work of missionaries & the ruling classes would be educated in those institutions
Nationalism & a weak sense of attachment to the wider Ummah has been the result of this as well as lack of connection to Islamic history, and greater connection to national history.
However, more than this type of preaching, in our times I think it’s big businesses with local branches, promoting certain messaging,using advertising & media to change ppls attitudes
We must rebuild schools, institutions, media..