Because the When an item/file is deleted are triggers, you are limited on what you can capture from them. Currently, When an item is deleted triggers it only captures six parameters for use.
When an item is deleted it it offers six parameters to use within the Send an email (V2) action (see the subject and body areas):

When a file is deleted it offers six parameters to use within the Send an email (V2) action (see the subject and body areas):

If you'd like expanded built-in functionlity added to Flow, please consider submitting it to the Flow Ideas page, where it can be voted on by other users, and tracked and commented on by the Flow team.
You do have some alternatives, however. The connector does have a DeletedItemList Parameter available to it. So, you can invoke it as an Object Variable for usage within your Flow (such as passing it through to the email).

You'd have to do some testing to see what the DeletedItemList variable returns. If it does return the item creator, then you could grab that and also pipe it into the Send an email.
For more information on how to utilize variables, review the Create variables for saving and managing values in Azure Logic Apps documentation.
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