Here are my 2 cents .
1. Spirituality like science is a field where documented logical experiences of well meaning wise people (whom we may call scientists or even philosophers) should be held authentic and right . Heretic / unscientific / untenable individual experiences howsoever in majority do not hold water against the authentic empirical documented experiences of well meaning wise people (whom people may call scientists or philosophers)
2. The religions world over and of all ages have accepted that there is life after death though there may be difference in how they present it ( like existence till judgment day in Christianity , Qayamat day in Islam , Worship of ancestors in confucianism / buddhism/hinduism , re-incarnation in hinduism / buddhism) . So all are unanimous without exception that spirit in human being is part of super spirit / cosmic spirit / all pervasive spirit and it exists after death . Let's first agree to agree on this fundamental experiences of philosophers of all age and region .
3. There were some questions why so many conflicts then and what was the need for so many differences etc. This is wonderful question . Before I answer this, let's examine how human beings play sports . If we were to see all game of sports (say from animal perspective or anybody not knowing that sports itself) , they are all follies . Some people chasing 1 ball trying to put somewhere and eliminate some sticks etc . But as anybody and everybody on this forum would agree that sports is for mental and physical development of participants . It induces a spirit of sportsmanship in a good person . Sports man has to know the rules of the game (his/her limits /restrictions / privileges /rights etc) . And there indeed is great fun in playing the game.
So coming to answer why so many conflicts / multiplicity in universe , God or super spirit as one may call it - felt alone and wanted to play. So He created multiple versions of His and started playing. Rules of the game are all sciences (material/ social / ethical /spiritual) . And one has to attain maximum potential knowing / appreciating these wonderful treasures . This is well documented in following axiom in hinduism.
lokavat tu lila kaivalyam [Brahma Sutras - 2.1.33]
The creation is merely a sport of Brahman.
Ekoham Bahu Syam
The non dual Brahman -Cosmic spirit thought or willed, "I am One, let Me become many!" ; so by the sankalpa(ie assertion ) the Brahman projected himself as many.