Charles is not the Duke of Edinburgh. There is no Duke of Edinburgh. When Charles became King the Dukedom merged in the Crown and became vacant (or available so to speak).
That is why Charles could make Edward the Duke of Edinburgh.
For the news itself, it is not suprising. It is well known that Charles does not really like Andrew and Edward. There is a lot of resentment on his part.
He only likes his younger sister, Anne, and is quite intimidated by her. He grew up with Anne. He never grew up with Andrew and Edward like he did with Anne.
Charles loved his Granny, the Queen Mum more than he liked Philip, Andrew, Edward and even his own sons.
Elizabeth and Philip had two children in quick succession, then several years went by and they had two more children in quick succession. Not surprising that they basically function as separate sets of siblings. Especially since Charles had been shipped off to boarding school by the time the younger two were born - how often did he even see them when they were growing up? Almost more of a cousin-level relationship than a sibling one.
