For me, a large monitor is 60 inches, but I have not seen traders with such monitors.
The larger monitor size allows traders to view multiple charts, indicators, and other financial data at the same time, but all this does not require a large monitor.
I am comfortable with 2 monitors of 24 inches, but since I do not trade every day, I watch movies and YouTube on the second monitor.
60 inches is surely too wide, it is not a proper size for trading. Yes, it is only appropriate used for viewing the charts or displaying certain data. But since it doesn't really needed, it is unnecessary to have 60 inches monitor. I think 14-15 inches are enough for trading, it is the standard/common size for laptop monitor. Or if we want to have a larger size, a computer with monitor 18-20 inches is enough.
No, it doesn't have anything to do with the trading result but if it provides comfortability to the trader, well it could help them create better decisions.
It will be comfortable if the size is appropriate/suitable. But if the size is too wide, it won't be comfortable anymore. I am sure a professional trader won't choose a large monitor with nonsense size, they will choose a normal size that fits with the need of trading equipment.