Illinois bond ratings were recently down graded. This means that Illinois must pay a higher interest rate on bonds they sell. According to Illinois law Illinois bonds must be paid first before anything else gets paid.
This means that purchasing Illinois bonds are a great investment. They pay a better rate then other states and they will be paid.
Right now rates are the lowest they have been in decades. So the cost to the state is even less then when Illinois had much better ratings but paid a higher interest.
Selling bonds to raise funds for Illinois can help raise income to cover its debt at a very low cost to the state.