Why did McMahon go to a small line up in the 2nd half?

He had to get all the sharp shooters he brought in on the court bro

Because McMahon is terrible at making rotations.

I can try to justify it from his perspective. Vandy's best player, 7 footer Liam Robbins, was out. As such, we didn't need to match his length on the inside and Vandy was killing us primarily with guard play. Trae was playing extremely well so it made sense to give him minutes. I think McMahon was trying to match their small lineup and keep up with them. Manjon was killing us.

Then again, that is just me trying to justify it. I think McMahon's biggest weakness is his rotations. They haven't made sense all year.