It continues to surprise me that fans are reacting as if that's never happened before. It happened just a few years ago when The Clone Wars contradicted Karen Traviss's Mandalore novels. And it happened years before then, when the prequel trilogy contradicted what earlier EU novels had asserted about the events and chronology of the Clone Wars.
The Clone Wars references the prequels broke were generally fixable. And The Clone Wars
wasn't very good - I quit watching long before they introduced their version of Mandalore, so the books are all I have.
So really, why is anyone still surprised by this?
I don't think it's so much "surprised" as "disappointed". I can understand why they don't want to be beholden to the details, but adhering to at least the broad strokes would've been nice, leaving open the possibility of fixing things to match.
(I know that Lucasfilm started going in their story direction before J.J. Abrams was hired, but the fact that his Star Trek
jettison the old continuity almost makes it worse.)