Harry watched them go, feeling slightly uneasy. It just occurred to him that Mr and Mrs Weasley would want to know how Fred and George were financing their joke shop business when, as was inevitable, they finally found out about it. Giving the twins his Triwizard winnings had seemed a simple thing to do at the time, but what if it led to another family row and a Percy-like estrangement?
Harry Potter and the Order of the Pheonix
I think as was inevitable can be taken as "as it was inevitable, meaning because it was inevitable. Is my understanding correct?