I had $2300 of federal income tax withheld in 2020, why is my refund only $740?

You do not necessarily get it all back.   You get back the difference between the tax liability for your income, filing status, dependents, etc.  Some people get nothing back---or even owe more if they did not have enough withheld.

Why doesn’t my refund match my W-2?

The amount you see in box 2 of your W-2 is not necessarily your tax refund.  That box shows how much was withheld from your pay.  But like many others, you have a tax liability to pay tax to the government.  So the refund you get back is the difference between how much you have to pay according to your filing status, tax bracket, number of dependents, credits and deductions, etc. and the amount that was withheld.