none of the T20 World Cup winning squad players are with India in this series.
Incorrect. Sanju Samson, Shivam Dube, Jaiswal, Rinku (although he was in reserved player list) were part of t20wc squad and also part of this series squad.
India bowled well in the beginning but could not bowl well towards the end otherwise they could have won the match by a huge margin.
Dube and Abhishek who are still work-in-progress bowlers went plenty so it played it's part in this small margin victory.