Nets are a better team than some people give them credit for . No absolute superstar ( Russel is a legit All-Star but still ) but the team can go 10-11 deep without losing anything. They had i think the highest scoring bench in the league and it showed again against the Sixers. Nets have nobody that can go up against Embiid and if he was fully healthy he'd destroy them but since he isn't there is a shot for the Nets to win their series. Sixers also have some liabilities a good coaching staff ( that the Nets have ) can exploit.
Simmons can't shoot so you don't need to guard him on the perimeter and Reddick has no chance to defend any of the three Nets scoring guards . So the gameplan in Game 1 was to complely sag off Simmons on defense and to attack Reddick on offense every chance Russel, LeVert , Dinwiddie had and it worked to perfection.