Take a look at the original sentence again:
Quang wants a degree in business administration,
he fantasizes about yelling at future employees who are too afraid
of losing their jobs to talk back.
You wanted to fix it this way:
Quang wants a degree in business administration,
because he fantasizes about yelling at future employees who are too
afraid of losing their jobs to talk back.
When you have two main clauses joined with just a comma, you can fix the problem by subordinating one of the main clauses. Because is a subordinate conjunction that will do this job. When because comes after a main clause, however, you do not need a comma in front of it. An important rule to remember is that 99.99% of the time, there is no comma before because.
You might want to consult the rules for fixing comma splices and fused sentences.
Go back to the sentence to try again.