A traditional 8 week training camp usually consists of 6 weeks of insanely intense 3 a day workouts, a fighter will generally peak at the end of week 6, week 7 will consist of lighter 2 a days so they don't burn out, week 1 will consist of light sparring, light grappling, and a little cardio.
You can't peak after being in the gym for 2 days and then hitting a press promo tour.
Look at Chris Weidman, he's a cardio machine. Go back and watch his fight with Demian Maia, he took that fight on a week notice and looked like absolute shit and was gassed out from the start. Mendes ain't the first person who's known as having great cardio that has looked like shit taking a fight on short notice.