Why is my refund so much

[DMarkM1]

This year the answer most likely is you are eligible to receive the Recovery Rebate Credit.  This credit is refundable, meaning if you qualify for it, it will be added to your return on top any regular refund amounts.  

During the interview in TurboTax you would have been asked what, if any, stimulus payments you received in rounds one and/or two.  Those amounts would have been automatically subtracted from your total eligibility amount with the remainder added to line 30 of your Form 1040.  

Here is a link with more information on the Recovery Rebate Credit calculations and eligibility.