It is demonstrated in the Vedas that Krishna develops the desire to help others, and that might be expressed in many many   ways .

The Jivas have always been, but it can be understood they are ” expressed ” or “manifested” from Krishna.  As Srila Jiva Goswami in Tattva Sandarbha says, Krishna is  inconceivably making the impossible possible. The living beings are simultaneously and inconceivably one and different , this is how the philosophers of Gaudia Vaisnavism explain these truths . It appears and is my  understanding that some of the Jivas originate  from Maha Sankarsana , and some from Mula Sankarsan, some of  those who appear from Maha Sankarsan, are unable to reach out in  spontaneous love with Krishna. 

Maha Sankarsan then at a point manifests as Mahavisnu  ,  He  displays a  helping mood of the Lord , consequently  I would posit , Maha Visnu takes those Jivas from the tastasta brahman , who could not spontaneously love Krishna and who are stationed in the spiritual impersonal energies . Those  who originated from Maha Sankarsan . Because God  is all-knowing and wants to help them understand the feelings of relationships and rasa , He  gives  facilities for activities,  because they can not act spontaneously in love with Him directly they act materially

 “A pencil of light “, that I believe Srila Narayana Maharaja refers as the Jivas entering into Maya …from Sambu, sounds like they are arriving from somewhere , 

In that sense, Krishna as Maha Visnu is  manifesting and arranging the facilities and the ultimate rescue of the Jivas with His rectification programme that can take endless cycles. The Maha kalpa .

 Visnu appears in many incarnations to rectify and attract the lost souls .

In that way, Maha Visnu remains a functional form who exhibits the facilities, but  from Him come  other incarnations come to help the jiva .

Jiva Goswami indicates in the Tattva Sandarbha the Jiva is the cause of the material universes by their desire ,  Sadaputa would refer to a responsive universe,  with  many possibilities , akin to quantum physics. 

In that way  the origins of some of the  jivas are from Maha Sankarsan and then Maha Visnu Via Sambu  ,who  brings the tatasta jivas who cannot directly love Krishna , into the material realms to fulfil their independence and help them understand and  ultimately regain their original purpose. Its difficult to understand how God would impose death on Jivas without they themselves making a choice for false independence. 

Another question arises,  can Mahavisnu expand jivas , some of which can directly enter the spiritual realms, ?

 I believe He does not play that role 

Srila BR  Sridhar Swami ,  gives some references to the origins via tatasta and Brahman And Srila Gour Govinda Swami quotes Bhagavatam purport 4.30 .5 

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