Question

he explained how it was that hewas still alive 我知道it是形式主语 that后边是真的主语但是我还有问题

how it was 不就是 how he was still alive was how it was 这个句型啥意思

Answer 1

主语：He 谓语：explained
宾语（从句）：how it was that he was still alive. 既是宾语从句并且是一个强调句,
句式为：how he was still alive,意思是,“他是怎样活下来的.”但是特殊疑问句改为强调句：疑问词如why+is/was it +that +其它，如果这个特殊疑问句要做宾语从句，那么只需把is/was和 it的位置调就行了，就像陈述语序一样。

Answer 2

这里的it是引导强调句，强调句的形式：it is/was+被强调部分+that+句子的剩余部分.
how在强调句中的正常位置是：how was it that he was still alive.但在explained后当宾语，其从句的顺序就是：he explained how it was that he was still alive.这句话如果不是强调句，去掉强调句的结构：it is/was+被强调部分+that.....，它的顺序是：How he was still alive.---He explained how he was still alive.
大意：他解释他是如何还活着的原因。

Answer 3

it是that引导的句子的形式主语。正常的语序是 that he was still alive was how, that 从句后置了，前面加个形式主语it

Answer 4

可以看成：
He explained (how it was) that he was still alive.
这句话是宾语从句，他解释他是如何还活着的。
关于it，应该是 it was that he was still alive.