HildaCrypt was created for fun
https://www.bleepingcomputer.com/news/security/hildacrypt-ransomware-developer-releases-decryption-keys/
The developer behind the HildaCrypt Ransomware has decided to release the ransomware's private decryption keys. With these keys a decryptor can be made that would allow any potential victims to recover their files for free.
When a new ransomware or a variant is discovered, it is very common for researchers to post about them on Twitter. This week, researcher GrujaRS discovered a new ransomware variant and identified it as a STOP variant.