The Rafidah Shi'ah have historically been the facilitators for other subversive factions, as Ibn Taymiyyah mentions (Majmoo' 13/209-210), that:

لكن الخوارج دينهم المعظم مفارقة جماعة المسلمين واستحلال دمائهم وأموالهم والشيعة تختار هذا لكنهم عاجزون والزيدية تفعل هذا والإمامية تارة تفعله وتارة يقولون لا نقتل إلا تحت راية إمام معصوم والشيعة استتبعوا أعداء الملة من الملاحدة والباطنية وغيرهم ولهذا أوصت الملاحدة - مثل القرامطة الذين كانوا في البحرين وهم من أكفر الخلق ومثل قرامطة المغرب ومصر وهم كانوا يستترون بالتشيع - أوصوا بأن يدخل على المسلمين من باب التشيع فإنهم يفتحون الباب لكل عدو للإسلام من المشركين وأهل الكتاب والمنافقين

However, the kharijites, their venerated deen is to separate from the jamaa'ah of the Muslims and to make permissible [the shedding] of their blood and wealth. The Shi'ah also choose this [course of action], but they are unable [practically], and the Zaidiyyah do this, and the Imaamiyyah sometimes do this, but sometimes they say "We will not fight except under the banner of an infallible Imaam", and the Shi'ah entice the enemies of the religion, amongst the atheists, the Baatiniyyah and others besides them. For this reason they counsel the atheists - such as the Qaraamitah who used to be in Bahrain, and they are the most disbelieving of the creation, and the likes of the Qaraamitah of the Maghreb and Egypt, and they used to conceal themselves behind Tashayyu' (beliefs of the Shi'ah) - they counseled them to enter upon the Muslims from the door of Shi'ism, for they (the Shi'ites) open up the door to every enemy of Islaam, amongst the Mushriks, the people of the Book, and the Hypocrites.

The Qaraamitah, Baatiniyyah believe that religion is just a veil and is for the common folk, whilsit the higher esoteric truths are known through gnosticism and philosophy. So to deceive the Muslims, they wore the veil of Shi'ism to gain proximity to the Muslims and to call them to their disbelief.