Grappling endurance depends on aerobic capacity, local muscular endurance, and efficient technique. Build the aerobic base, add grip and isometric work, and do position-specific rounds. Wasted tension is the biggest drain on most beginners.
New grapplers grip too hard, hold their breath, and use maximum effort in positions that require very little. This produces enormous, unnecessary energy cost. Experienced grapplers in the same round often work at a fraction of the intensity while achieving more. Technical improvement is the single largest contributor to grappling endurance, and no amount of running substitutes for it.
Dead hangs, towel-assisted pull-ups, farmer's carries, and gi or towel holds all build the sustained grip that grappling demands. Isometric holds in relevant positions, such as a long front plank or a held bottom position of a row, develop the ability to maintain tension without moving.
Rounds spent working from a single position, such as escaping bottom side control or maintaining top pressure, are more useful than generic circuits. They train the specific muscular endurance and the technical efficiency at the same time.
Breath-holding under pressure is almost universal early on and it destroys endurance. Practise deliberate exhalation while working from bad positions. It is a trainable skill and it changes how long rounds feel.
Grappling is demanding on connective tissue and the nervous system. Three or four hard sessions a week with genuine easy days between them will take you further than daily maximum effort. See Exercise Physiology and Energy Systems and Recovery Science and Adaptation.