It is meant that if they don't prepare, they die.

理解句子，首先要考虑动词的用法和句型，要学会动脑子。网友应该知道这个句型是怎么变来的吧：It is said that ...  上面的句子跟它是一个道理。

mean 的其中一个用法是，接宾语从句。例如：

I mean that...

He means that...

We mean that...

They mean that...

你把上句改为主动语态，一种可能的变法，就是：

It is meant that if they don't prepare, they die. =

We mean that if they don't prepare, they die.

（我们的）意思是，如果他们不作准备，他们就死。