This is showing that the Dave Ramsey "debt snowball" (pay off smallest debts first to get a psychological win and some breathing room by having fewer minimum payments) is a more effective way to get people to pay off many separate debts than paying off "highest interest rate first" even if it is less optimal for a rational actor. Just another case of people aren't 100% rational that many people have known for a while…
I have literally have people tell me that this is still rationality because it's the rational thing "for them". Like, the weirdest one was a cognitive psychology doctoral student. I mean, okay, if you can redefine rationality to be completely subjective, then sure, rationality is flargikriggendurf.
Optimizing the likelihood of consistently following through with a plan is very rational.