All Muslims must be grateful to Allah, The Glorious, Who guided them to The True Religion, Islam, and to the Prophet Muhammad (SAWA) who conveyed the message of Allah despite all the hardships and difficulties and torture, and to Ahlul Bayt (AS) who preserved the message and kept it intact by their great sacrifices including their lives to defend Islam.
Islam was never spread by sword of governments or armies but by the true evidence.
The governments of the opponents of Ahlul Bayt did everything to prevent Muslims from knowing or following Ahlul Bayt and forced them to follow other sects. That is why you see spread of non Shia sects under the governmental propagation and orders while followers of Ahlul Bayt under pressure and torture. Yes, millions of Muslims who came to know about the true Islam, left those sects and became followers of Ahlul Bayt (AS). Most of Iran was following those sects of those governments away from Ahlul Bayt but after centuries, and by efforts of sincere scholars, they found the real teachings of Ahlul Bayt and followed them. They are grateful to Allah who guided them to the true Islam.
'They are till today many Iranians who follow those sects spread by anti Ahlul Bayt governments. After all, all Muslims following any sect are Muslims.