Hi Stuart,
ClickDimensions does not search deactivated leads to match activity to them. However, you can email deactivated leads. So these new ones are being created because they clicked on a link in the email and all it knows about them is their email address.
I would suggest keeping these leads active but maybe giving them a different status somehow to tell you they are not interested at the moment but might be in the future.
Thank you for using the forum!