Henderson had only proven himself at small EPL club/lower league level such as Sheffield United, Grimsby, Shrewsbury and Stockport. His CV makes him a 2nd choice goalkeeper at a top club. So really there's nothing that justify his arrogance especially when our 1st choice GK happens to have a record number of Sir Matt Busby awards.
That's why I was always against hyping kids as its so easy for them to believe their own hype. Unfortunately United lack the structure to acknowledge that. Nobodies are given ridiculous contracts both in term on longevity and salary, we had a manager (can you really call Ole a manager though?) who guaranteed him a 1st team place even though he already had the highest paid goalkeeper in the world at his disposal and the fans do not help either. Just look at Garner whose already been considered the next big thing simply because he did fairly well in the long ball/rugby league. There's a huge gap between playing well against the likes of Helik, Travers and Norwood and playing well against the likes of De Bruyne, Salah and Haaland.