This incident happened in the last over of Axar Patel and in the 14th over of RCB's innings when Maxwell hit the ball in the air, trying to hit a big shot on the first ball of the over and Shreyas Iyer, standing at deep midwicket, dropped a simple catch.
After this, R Ashwin, fielding at short third man on the last ball of the same over, left a simple catch and rubbed salt on Delhi's wounds. Even if a single catch of Maxwell had been held on to, then perhaps Delhi could have easily won this match, but dropping Maxwell's catch proved disastrous for them.