Fundraisers that were a pre-existing WordPress user, the user isn't required to provide their first and last name. As such, relying on it can result in blank names — which is what's happening. Users in WP have a display_name property which guarantees to always be something. I
can
be a username or something, which would be weird, but it's the most reliable.
An alternative would be to check if a user creating a fundraiser profile has their first and last name set, if not then we request it. Keep in mind, though, that folks can always remove their first and last name in the WP user profile page. 🤷‍♂️