In English sentences, main clauses and subordinate clauses are clearly distinguished.
The main clauses can occur independently, while subordinate clauses are attached to main clauses. Therefore, two subordinators cannot appear in the same sentence, as a sentence without the main clause is ungrammatical in English.
→ the sentence *"Because he got up late, so he was late for school." is ungrammatical.
On the other hand, the "main clause-subordinate clause" principle is less rigid in Chinese. Thus, the main function of the connectors is to mark the semantic relationship between two clauses. As a result, adverbial connectors can be placed in sentence initial position, after the main clause, or appear in both positions at the same time.
(因為)他很聰明，所以讀書讀得很好 (He is smart, so he is good at academic work.)
( 雖然)他很聰明，但是讀書很不努力 (He is smart, but he is not very diligent.)
