I wonder if the word "that" is used as a demonstrative pronoun or relative pronoun. I am very confused because of the commar used in front of "that". I learned that "that" is not used with undefined relative pronoun with "comma" before it. So would it be possible for me to understandt "that" is a demonstrative pronoun despite the usage of error of comma. I chose this sentence from LOCNESS learner corpus by native students.
"Boxing is a high risk, short term career the men who do it are aware of this, that is why they are paid so highly".