see, actually, the thing is that most of the time a gender transition isn't shocking to the people around the transitioner. and, that's kind of the point. in situations where it is a surprise, it should maybe be questioned extra rigorously.
my sister's response, verbatim: "obviously. what took you so long?". not only was there not an expression of shock, but there was actually an expectation that it was coming.
my dad was initially confused, but he admitted afterwards that he just didn't know a thing about it and that he would have probably seen it coming if he did. he did admit to being aware that i was queer in some way.....but he didn't want to make assumptions, either. he had some expectation, but he didn't really know how to frame it.
i had guy friends admit that they basically always saw me as a female friend. it was stuff like "well, you were basically always a chick and we did realize it, we just never really thought about whether you were going to like actually be a chick. you were just being j." . this idea that "j is different because j is j and j is different" was cemented across a network of people, and just not questioned. again: the concept was blurry, but the realization was apparent. and, it wasn't a shock so much as it was an explanation.
that's the point, right. one does not become somebody that never existed on the other side of it, like it's a metamorphosis. rather, one aligns with what they always were in the first place.