Batting first, Maxwell's innings and captain Aaron Finch's 69 off 44 balls catapulted Australia to the huge total of 208/4. Agar then wreaked havoc.
Left-arm spinner Ashton Agar picked up a brilliant five-wicket haul, including a hat-trick as Australia defeated South Africa by a huge margin of 107 runs in the first T20I.
Chasing 197 at the Wanderers Stadium on Friday night, the Proteas were bowled out for 89 runs – their lowest total in T20I cricket.
Put in to bat, Australia lost David Warner to just the second ball of the innings for 4 with veteran pacer Dale Steyn extracting some steep bounce from the surface to take the top edge of the opener’s attempted pull shot.
However, skipper Aaron Finch and Steve Smith then joined forces and built an 80-run partnership in 48 balls. The duo was also helped by some poor short-pitched stuff from the South African bowlers.
Finch scored 42 runs before he became the first scalp of Tabraiz Shamsi. Matthew Wade and Smith however continued with the free-flow batting and collected runs with ease before they both went back to the pavilion in space of three deliveries, for 18 and 45 respectively.
Mitchell Marsh (19) and Alex Carey (27), the next batters, did just enough to keep the momentum going. However, Agar made his first impact on the game with the bat as he picked 18 runs from the final over of the innings and helped Australia set a total of 196/6.
The total then quickly turned out to be more than competitive as South Africa lost captain Quinton de Kock in the very first over of the chase bowled by Mitchell Starc.
That dismissal just set the tone as the host lost wickets in a flurry. They were four wickets down after seven overs and were already looking down the barrel.
However, the worst was yet to come as Agar proceeded to remove Faf du Plessis, the only batsman who had shown resistance up to now, for 24. He then removed Andile Phehlukwayo and Steyn to become the second Australian bowler to pick up a hat-trick in the T20I cricket.
He nearly made history after taking another two wickets with consecutive deliveries. However, it was only the smallest of margins which denied him becoming the first bowler to record two hat-tricks in the same T20I. Despite that, he finished with figures of 5/22 and was the tormentor in chief.
Leg-spinner Adam Zampa picked up the final wicket to leave South Africa all out for 89 in just 14.3 overs.
The two teams will now face each other in the second T20I on Sunday at Port Elizabeth.
Brief Scores: Australia 196/6 (Steve Smith 45, Aaron Finch 42, Tabraiz Shamsi 2/31); South Africa 89 all out (Faf du Plessi 24, Kagiso Rabada 22, Ashton Agar 5/22)