The state refund was significantly smaller than the number turbotax gave me.. Why?

Look at your state return to confirm the amount of your state refund as it was filed.  

If your state tax agency lowered the amount of your refund, you'll need to talk to your state tax agency for more info about it.  They should send you a letter in about 3 weeks or so, but you can phone them for faster info.

FAQ:  How do I contact my state department of revenue?
https://ttlc.intuit.com/community/state-taxes/help/how-do-i-contact-my-state-department-of-revenue/01/25573

The state does not notify TT, so wait for the letter from the state.  Could you have made a data entry error, or forgotten to claim some income?

No, I haven't made any errors, this was a first time for me having done my taxes online through a service so I was extra careful. Disappointing to say the least. Though, thank you for your input.

Post back after you get the letter from the state.