I'm assuming because I was trying to see all avenues for tax breaks it popped up. My return this year is less than 2019, so Turbotax asked me if I wanted to use 2019's return. So I clicked it, thinking I could just delete it after viewing it if it wasn't applicable to me (similar to how if you start a W-2, you can review, edit or delete it). I'm not sure if this is why, but it's the only thing I've done differently than other years.
However, I quickly realized I wouldn't qualify for the method of figuring out deductions I had just selected because I didn't save every receipt for 2019, so I backed out of it.
I live in Florida, if that matters.