He has the toughest schedules ("two of the top five") including last year and 2013. Let's look specifically at the 2013 schedule v. the 2018 schedule. 2013 is worse (only .558) than 2018 (.573).

Sagarin disagrees (#38 in 2013, #69 in 2018), so let's see if we can figure out why?

In 2013 you guys played UVA, Texas, Utah, MTSU, USU, GA Tech, Houston, Boise, Wisconsin, ISU, Notre Dame, Nevada, and Washington.
In 2018 you guys played Arizona, Cal, Wisconsin, McNeese, UW, USU, Hawaii, NIU, Boise, UMASS, NMSU, Utah, and WMU.

Feel free to look up the records and the records of the teams they beat. I'm not the stat wizard Indy is, but there's a reason Sagarin liked your 2013 schedule so much more DESPITE the fact that they had a worse W/L record.