What competition?
Someone of a similar profile coming in would be competition.
Donnarumma is a couple of years older but on among the highest wages in the team (and league) and was made undisputed #1 the moment he walked in. That's not competition. If it were a normal job it'd be contrusctive dismissal to have someone paid 5x you come in and take 90% of your hours. No amount of "backing yourself" is going to make up for that.
The club had a plan, replace Ederson with Trafford with a year crossover, and then they aborted that plan when Donnarumma came onto the market. That's fine, it happens sometimes, but Trafford has every right to feel hard done by and resume his plan for his career, which involves starting every week for a CL club. Newcastle will likely come back in for him, and everyone will pretend the last 5 months didn't happen.