The search for Fungie: Ireland's beloved bottlenose dolphin who has gone missing after 37 years
https://edition.cnn.com/travel/article/fungie-dolphin-ireland-intl-scli/index.html
The dolphin must have felt intimacy with audience. That's why Fungie didn't run away. But, I guess Fungie wasn't served enough food during pandemic. It could have brought him to run away.
It's one possibility. Another possibility is that dolphin sought place to die. It's the last thing we would like to imagine.