Cardio Disappeared

I've been training BJJ for about 2+ years, and this year has felt pretty bad. I used to be able to go for a several hours, but now I can't even finish a 40 minute lesson.

I'm completely gassed to the point where I can't even move my limbs, much less do any meaningful rolling, causing me to miss out on precious mat time.

Nothing has changed from then to now. My diet hasn't changed, and my sleep seems fine. Anyone else experienced this? What's going on?

EDIT: The only major thing that has changed is that I switched from a calisthenics routine to weightlifting? But can that really affect cardio that much?