what was it that made you decide to choose this company? 在这个句子中,that 是构成强调句的that, 这是特殊疑问句的强调句形式.把 it was .that 去掉后,句子仍然意义完整.
But people say that in this company .此句中的that 是引导宾语从句的连词 that.