I think that even if he was afraid it wasn’t because he was surprised as much as it is scared to see if the audience (Odium) would play into the game Hoid was playing, wouldn’t you be afraid if things went wrong and you ended up showing your hand instead of the bluff you had set out?
I would think Hoid has some Connection to the original vessels/shards and may have had some inkling as to what had occurred with the change in management of the Shard.