Apologies for the late reply. The asset was likely posted to Pixabay by the contributor. Contributors are not restricted from using other services to sell their images. Also of note is the image no longer appears on the Adobe Stock website.
So far, I have found two images that I created and uploaded to Pixabay in Spring 2016 on Adobe Stock uploaded by Mariephotos in 2020. I know my images are free on Pixabay, I don't expect for someone to get paid on another site. I expect more from Adobe.