Finally got a chance to watch this fight. Definitely changed my thoughts a bit. Kayla wasn't disinterested/unmotivated, she just ran into a beast of an opponent that she hadn't faced before. Pacheco was much bigger and much stronger than in their previous matchups. Kayla didn't have an answer. I'd also argue Pacheco both did more damage and scored more on the ground when she was on her back. There was one 1-2 minute exchange I believe in the 3rd round where Kayla was on top but clearly losing the exchange.
I think this is why Kayla is taking the loss so hard. She didn't get caught, she didn't overlook Pacheco, she got outwilled in the 5th and got beat in her best area. That's tough to get over mentally. Kayla isn't gonna get markedly better at takedowns before their next fight. My guess is Pacheco takes the next one even more convincingly. Outside of Judo Pacheco beat her everywhere.