关于曼哈顿语法其中一个句子的疑问

便签小祺

The clothes inside the store looked more appealing than did thoes outside the rack.
为什么不是
The clothes inside the store looked more appealing than thoes outside the rack did?这到底是主语对比还是？
还有什么情况是要把助动词放在主语前面的情况

请各位大神指点！！！谢谢