Delete Role Assignment

Hi All,

We have received an Azure activity logs in which the Operation Name is Delete role assignment and the Event initiated by is MS-PIM.

In which case the role is deleted by "MS-PIM" and what's the reason for deletion.

and also,

When we tried to fetch the logs through Log Analytics the Caller was some hexadecimal string, so is there a way to resolve that to the user name with log analytics query.