As a former amateur goalie at mickey mouse level, I like to delude myself that I have some insight into the goalkeeping mindset. Ahem.
Anyway, for what it's worth, my take is that a bit of competition is necessary to ruffle a few feathers but that this competition should only go on for a short period during which the acknowledged number one emerges. By the summer, at the latest, Carlo will need to make his mind up and stick with it. Goalkeepers are not like Mason Holgate or Ben Godfrey. They can't be pushed out of one position and compensated by being put into another. They are men apart, the odd men out. They need trust. Either they earn it - and you then stick with them through thick and thin (because every goalkeeper who ever played blunders now and then) - or you replace them permanently. I think Pickford will eventually emerge as our acknowledged and established number one - or he will start a slow descent down the league taking in places like West Ham, Crystal Palace, and Derby.
One thing is already clear. Olsen had his chance and blew it spectacularly. He will get less leeway for two reasons: 1, he is an acknowledged number two as his experience at Roma proved, and 2, he cost buttons. The only question in my mind is whether Pickford has the gumption to mature quickly enough to accept the open goal presented to him yesterday.