Tax law changes from 2018 to 2020

When the trump tax law went into effect, we were hit with a large tax burden and had to pay a lot extra.  We subsequently added more to our withholdings to compensate.  Last year (2019) we had a small refund, but this year (2020) we have a very large refund.  Our income did not change appreciably, nor did anything else about our taxes.  What, if anything, changed over the last three years?  We would like to reduce our withholdings, but not sure where taxes will be next year, i.e., we would rather have the money in our paychecks instead of a large tax refund.