Usually more income = more tax = less refund. Your withholding didn't increase enough to cover the tax due. Or some credits you got are reduced because you made more income. And any dependents you have are a year older. If you made more income that can reduce some credits you got like the EIC.
Here's a good FAQ on why your refund might be less than last year
https://ttlc.intuit.com/community/refunds/help/why-did-my-refund-go-down-compared-to-last-year-s/00/...
