It sounds like you had an insect problem, but it is hard to tell. It could have been a fungal disease.
Grass is a tough plant and can survive insects if it has a strong root system, enough nutrients, sun, and water.
You can go through the steps to reseed your lawn, then follow the “best practices” that turf science research has shown to be successful
Do you have at least 7-8 hours of sun on the area? Less than that means you will probably need to reseed every spring.
Conduct a soil test to determine how much fertilizer is needed each season-
Follow the steps to prepare and reseed the bare areas-
When grass is 3.5 to 4 inches high, begin mowing. Best practices research recommends leaving the grass no shorter than 3 inches tall. A long leaf blade means a deeper root system, better able to withstand heat and insect feeding.
Follow the recommendations here and begin following your soil test fertilization schedule-
Reference on insect pests and how to detect them-
Reference on lawn diseases and how to manage- http://www.msuturfdiseases.net
I hope this gets you started. If more problems occur, please take some pictures and write us again. You may also call the free MSU Garden Hotline during business hours at 888-678-3464. Thank you.