Is there a way for Miro to change the admin on the account to one of the existing team members?
While, yes, they could of course do so, whether they would take action would likely depend on your scenario.
For example:
If you have a paid subscription, then you could request this change by opening a support ticket.
If you are using a Free Plan, you have options to resolve this yourself:
Someone creates a paid subscription by going to www.miro.com/pricing. They will now be a Team Admin of this space. They would continue to maintain it as a paid team and invite other users, paying for a license for each of these new users. Or, then could cancel the subscription, downgrade it back to free and invite other team members to this new space as free users. Then everyone moves their boards to this new team space, and you promote 2-3 other users to the role of Team Admin!
You could also follow the steps outlined in this post (referenced in my previous reply) to create a new free plan team, invite users, and move boards to the new team.