Because Costumes inherit the Talent Grid of their underlying Hero instead of taking Emblems directly.
More on that here: Hero Costume FAQs! Please read for answers to most questions before posting new questions
Hmm, well, your options are to leave them on White Rabbit, or reset them again and put them back on Rigard.
Both are sort of unfortunate choices, but for what it’s worth, I get a massive amount of use out of Rigard, both in and out of Costume, and think he’s well worth having Emblems on.
On the plus side, you can choose a Talent Grid path that you’re happy with for him as both a Cleric and a Ranger — you may want to balance the nodes a little differently than you had originally.