这个句子是不是病句,它好像有两个谓语动词?

to affiliate himself with Nazis was something even he had to have known was not advisable.不是病句.
To affiliate himself with Nazis （不定式短语主语）was(谓语)something .翻译为：把他自己和纳粹联系起来是一件事.
even he had to have known was not advisable其实是修饰something的定语从句,即他早该知道这是不明智（的事）
另外,对省略的关系代词,我和1楼有点不同看法,当先行词是不定代词all, anything, everything, something, nothing, little, few, much, none等时,一般用that.所以这里才能省略.
通常情况下what不可省略.