Federal refund change

I have had no major financial changes since filing my 2019 return.  My income and withholdings have been relatively flat.  My issue is that my 2019 return showed a $1,175 refund while 2020 return shows $411 tax owed.  My state from 2019 to 2020 both were/are refunds ($517 for 2019 vs. $455 for 2020).  What could have changed?