应这样分析：

I（主语） wonder （谓语）if it’s because I haven’t been able to be outdoors for so long that I’ve grown crazy about everything to do with nature.（宾语从句）

在if 宾语从句中，又包含一个带有原因状语从句的复合句，而且这个复合句中的原因从句被强调。还原后宾语从句为：

if I’ve grown crazy about everything to do with nature because I haven’t been able to be outdoors for so long.

整个句子还原后是：

I wonder if I’ve grown crazy about everything to do with nature because I haven’t been able to be outdoors for so long.