can you please tell why author used comma in the following sentence? If it was necessary, can you please explain why? I got this line from a book about art theory
"One of the main problems facing Gombrich when he started his scholarly career was the uncritical acceptance of the idea that the figurative artist produced images of what he saw , with the qualification that through historical time and across cultures people have seen differently"
If you can give an example of similar usage of comma that would be really helpful. Thanks