Question

请问一个关于英语的问题~

It's the answer that led those who've been told for so long by so many to be cynical and fearful and doubtful about what we can achieve to put their hands on the arc of history and bend it once more toward the hope of a better day.

by so many是什么意思？如果by是表别动的对象的话，那么many是指代人了，可是怎么能用so修饰呢？
后面是answer的定语从句，但是let后面好像没有宾语....后面都是不定式
可以的话分析一下句子成分，先谢谢啦~
so many 可以表示很多人？真的吗？many可以做代词，那么so可以做形容词（adj）吗？

Answer 1

第五个词是led（lead的过去式）吗？
1.answer that后面都是修饰成分，led的宾语就是those，指“那些...的人”。
2.told for so long by so many是插入语， so many可以表示很多人，也可以表示很多次。去掉插入语后句子为：“who've been told to be cynical and fearful and doubtful about...”
3.be cynical and fearful and doubtful about的宾语是what we can achieve
4.who've been told for so long by so many to be cynical and fearful and doubtful about what we can achieve都是修饰those的宾语从句，去掉后句子为：It's the answer that led those to put their hands on the arc of history and bend it once more toward the hope of a better day.
翻译为：是这个答案使那些人把他们的手放在历史的弧线上并把它重新拨回到通往美好明天的道路上。

整体翻译一下：是这个答案使那些曾被长期教导要对我们所能做到的一切都持批判、恐惧以及怀疑态度的人们把手放在了历史的弧线上并把它重新拨回通往美好明天的道路。

so可以用作形容词，表示如此的、这样的。

Answer 2

by是表示被动语态的动作发出者，many是指代人，译为：由如此多的人。answer在定语从句作主语， led 的宾语是those 。It's the answer是主句，that led those who've been told for so long by so many to be cynical and fearful and doubtful about what we can achieve to put their hands on the arc of history and bend it once more toward the hope of a better day. 是定语从句
变为简单句为the answer led those 。