Even if you want to say he owns a couple of extra losses due to that defensive style, it is frankly ridiculous and shows a clear bias against him to say he owns the whole situation. That 20-15 team was our first team to not beat a SINGLE top 25 team all year in 40 years, and Underwood lost Tracy Abrams, Coleman-Lands and Malcom Hill before he set foot on campus. The 2017-18 team would have been awful with Groce or anyone else at the helm, as well.
The fact you are throwing the "all-time loss leader" out there so often speaks to a bias, IMO, as well. That team (2018-19) was bound to take a step back, as well, losing Finke and most importantly Leron Black and having to rely heavily on freshmen and newcomers. And by the end of the year, they were showing signs of improvement, knocking of #13 Maryland and #9 Michigan State, not to mention Ayo turning into a young star. The 2018-19 team was building up to the 2019-20 success, and absolutely everybody knows that.
You can knock on Underwood for the 2020-21 upset and last year all you want; there is plenty of ammo. However, holding the first two years against him is completely insane.