此话如何理解，句子结构是什么

Suddenly last week,however,facts came raining down,in effect making further scientific debate on what mainly causes the problem all but irrelevant.
不知道在这里发帖子对不对~~~~

[Suddenly last week],[however],facts came raining down,[in effect making (further) (scientific) debate on (what mainly causes the problem all but irrelevant.)]

然而上周突然大量事实涌来，结果引起进一步争论：主要是什么引起了这个几乎不相干的问题的。

二楼分析得不错，
不过句子主干写facts came为佳。