Didn’t the thousands of students of Bais Shamai follow Bais Shamai? These were Tannoim, Tzaddikim, like malochim! Where they wrong? R’ Tarfon lied down to say kriyas shema like Bais Shamai. If it was wrong, why did such a great Taana do so?
(BTW – would R’ Tarfon need to say over kriyas shema since he did not do it in the manner of Bais Hillel which is the halacha? In other words, did lying down “passel” his shema, like eating matza without heseiba, one must eat again the matza in the proper manner?)