这是因为not only放在句首,后接句子时要借助助动词用倒装结构，比如：

Not only does television appeal to those who can read but to those who can't.电视不仅吸引阅读的人,而且也吸引了不会阅读的人.

Not only was everything Albert Einstain had taken away but also his citizenship was deprived of.爱因斯坦的财产不仅被掳掠一空,而且他的德国国籍也被剥夺了.

Not only had the poor man been fined,but also he had been sent to prison.这个可怜的人不仅被罚款,而且还被送进了监狱