Im gonna have to read Shakespeare's Julius Caesar to better understand that reference ds9 did but even without that I can deduce a theme about. Garak takes issue with the play first of all because he is Cardassian and they get taught that the state is never wrong. Not only that but his father and mentor figue was the most pwoerful man in the obsidian order, maybe even all of cardassia (or he would seem like that to a young garak). He even got to retire. So he does seem infallible to Garak.
Unlike Cardassia which is like yes the state is always righ yes cardassia will always win all wars, Humans have a long list of literature that illustrates how all humans are fallible even those in great power. Even great and smart leaders. Despite Cardassia being obviously so much bloodier, this is a surprisingly innocent view to have. Which is freaking fascinating because Julian and Garak's usual dynamic is being inverted. It is especially fascinating to have it after the "to think you still don't trust me. There is hope for you yet doctor" episode. Julian would usually be the one to believe in people's better half, making him look the more naive and innocent one compared to Garak, who is older and has done terrible things, schemed, lied, betrayed and killed people. The dynamic is inverted and everything still feels perfectly in character somehow.
Now picture it with me, the first time a person has that idea of the world shattered is when they look at their father one day and he is no longer the strong and infallible figure you believe he is as a child. That is the first time you know he is just a man. Seems that Garak literally never had that moment in his life. He has never seen Tain fail until the events of the die is cast because this is a particularly conniving man. Always a step ahead of everyone else etc etc. Now he is an old man reminiscing of younger glory days, Garak still looks at him as if he still is all that all the way up to when the operation fails.
It's interesting that they paired him up with Odo for this episode for obvious reasons. They sympatize with that feeling of wanting to go home in each other despite everything. Despite Odo choosing to stay on DS9, knowing what the founders are doing is wrong, he still always wanted to find his people and his home. Despite everything Garak has done so far, saving Natima and her students, helping rescue Kira, when presented with the chance to go home to Tain, not just to Cardassia, he couldn't not take it.
