English long difficult sentence translation, translate the sentence I underlined, don't use translation software, thanks!

Contemporary people would not understand the meaning of these words because understanding of them was erased from memory during the era of the Great Purge that followed the alien occupation of the planet.

Subject: those words

Predicate: mean nothing to

Object: the people of today

Participle: on account of guides all the words that follow to form a clause, which as a whole is a gerund, stating the reason for the predicate mean nothing

The fact is the object of on account of. Normally the fact should be followed by that or which, and then the understanding, but this sentence omits it. the understanding and the words after it are the cognate clauses of fact, which is a clause that complements the understanding of today

The fact is the object of on account of. the subordinate clause that adds to what the fact is.

on account of the fact that the understaning was wiped out.