I doubt that anyone is surprised by what is being revealed. The whole Trump campaign reeked of this stuff. What is surprising people is the way in which the case is evolving and in particular the fact that it looks like Mueller has indeed managed to get key people to incriminate themselves or cooperate. Things that had looked like they would not make it past the "it looks bad" stage may be approaching the legally provable, and others that looked like they would blow straight past Trump and his closest allies, are getting closer to the central players, and their scale is not diminishing to the trivial, or the coincidental.