Complex sentence: When Rabbeinu Tam became a great rabbi he did switch the order of the scripts and there are many sects in Judaism, especaly amongst the hasidim ", who after wearing the" tefillin of Rashi "wear the" tefillin of Rabbeinu Tam.
Split into simpler sentences: When Rabbeinu Tam became a great rabbi he did hold that the order of the scripts should be different. Today, there are many Jews, especialy amongst the hasidim ", who after wearing the" tefillin of Rashi "wear the" tefillin of Rabbeinu Tam.