Learn Russian: Благодаря тому что он знает язык, он нашёл работу. - Thanks to the fact that he knows the language, he found a job.

The preposition благодаря (thanks to) requires the Dative case. You cannot apply a case directly to an entire clause like он знает язык. Instead, Russian uses the pronoun то (that) as a bridge. You put то into the Dative case (тому) to satisfy the rule for благодаря, and then use что to introduce the rest of the thought. Literally, it translates to: Thanks to that, that he knows the language.

Could I use из-за того что instead of благодаря тому что here?

Grammatically it works, but it completely changes the tone. Благодаря is used specifically for positive causes, just like 'thanks to' in English. Из-за is usually reserved for negative causes, meaning 'because of' or 'due to a fault'. Since finding a job is a good outcome, благодаря тому что is the most natural choice.

Why isn't there a comma before что, since Russian usually puts a comma before it?

In Russian, commas separate clauses (sections of a sentence with their own subject and verb). The phrase благодаря тому что acts together as a single compound conjunction here. The comma is placed at the end of the entire dependent clause, right before the main clause starts with the second он.

Why do we use the perfective verb нашёл (found) alongside the imperfective verb знает (knows)?