It was decided (that due to the nature of the serials and demonstrations being made) that the Subjective Rating Scale would not be used.= It（the Subjective Rating Scale would not be used) was decided.Becausethe nature of the serials and demonstrations were being made.
所以我感觉,第一个that 从句是原因状语,第二个that从句是主语从句,就是it 代指的部分.