Question

Papaya has many each papaya seed can grow into a new tree however that does not happen why?

Answer 1

here is the first reason

here is the second reason

if all the seeds are sown separately with equal care and nutrition ,each will grow. however in real ,not all seeds are enough mature or even if they are , on soil they complete for nutrient once put together and mainly one or two comes winning.

Answer 2

If a plant develops seed to be dispersed by wind, a lot of them are blown into regions with very bad growing conditions, into water, stony bottom, regions without sufficient humidity.  

But not all seeds are transported into good soil, not all seedlings mature, some are damaged, others are eaten by animals, some are infected by pests, some simply rot.  

Therefore papaya produces such a lot of seeds to be on the safe site that - might be 1 or even 5% - of them grow up to healthy new plants and species survives.