Why did my ex spousal benefits increase from $225 a month to $1,021 after the death of my ex spouse ?
Unreduced divorced spousal benefits are calculated at 50% of the worker's primary insurance amount (PIA). Unreduced surviving divorced spousal benefits are calculated based on either 100% of the worker's PIA, or if the worker drew Social Security retirement benefits prior to their death, the unreduced survivor rate is calculated based on the higher of a) 82.5% of the worker's PIA, or b) the worker's actual benefit rate.
If you're also drawing benefits on your own record then Social Security would pay you your own benefit rate plus an excess divorced spousal or survivor benefit. The unreduced excess divorced spousal/survivor rate is calculated by subtracting either your PIA or actual benefit rate from the higher divorced spousal or survivor rate. Therefore, it sounds like your rate increased because your excess divorced spousal rate converted to an excess survivor benefit after your ex's death.