Not sure that is true. Based on the NCAA records, there has been a slight decline in the past 18 months in D1 schools found guilty of major violations. But 2016-17 had a much higher number of violations than any other years going back at least a decade. If 2019 is the start of a decline, it will be due to harsher punishments directed at coaches, more smoking guns due to cell phones/texts/etc, more money at stake for the D1 programs, and better enforcement agents.
Here are the number of D1 major violations per year - for all sports - as reported by the NCAA for the last decade:
2019 (six months) 8
2018 15
2017 20
2016 23
2015 13
2014 8
2013 9
2012 10
2011 15
2010 14
2009 13
Note: Each violation shown above represents one school that got nailed. It often was for multiple sports however.