Well, not exactly. Christianity was founded by quite a few people - Paul, the early church fathers, made popular by some Romans, and based on the writings that were supposedly based on the teachings of a man called Jesus. The evidence, as Rose has pointed out, is that if Jesus said what he said then it was directed to his own people - the Jewish population of the area around Galilee.
Wrong on both accounts, Rhi. By the time Paul came on the scene, the Christian Church had already begun to spread around the Mediterranean and possibly further afield than that. It was already established (though not in the sense that we understand the 'established church') as an entity.
As for "the evidence, as Rose has pointed out, ..."; if that was the case, why were the apostles willing to share the Gospel with non-Jews and to allow the church to spread out from Palestine? More importantly, why had Jesus been willing to share his teaching with Samaritans, Romans and other non-Jews. As far as I can make out from the documentation, the attempt to Judai-ify Christianity started some years after Jesus' death and resurrection and lasted for only a few years - it had certainly lost the argument well before both Peter and Paul died.
Paganism is for the whole of humanity because every people has their own indigenous beliefs, very often grown out of the local landscape and natural world.
Precisely, Paganism is very much territorial; it grew out of the local landscape and was therefore only relevant to people who understood that landscape. As such, there were and are a myriad of Pagan paths, which people are free to pick and choose from.
Now, I don't know whether you would agree that beliefs like animism and shamanism belong within the Pagan 'fold' - I have read material written by folk who regard themselves as Pagans that this is the case: but from what I understand Paganism is very much a 'pick and choose what suits me' belief system - not that different, in fact, to Hinduism.
Christianity may have a few teachings on 'looking after' nature; paganism generally has the created world as integral to its practice and a relationship with nature characterises many pagan paths.
If you study the Old and New Testaments, the passages have nothing to do with any cursory 'looking after' nature as you seem to suggest; it is an integral aspect of real faith.
I would happily accept that, over the centuries, that aspect of the Christian faith (not sure about post-70 AD Judaism) had been subsumed to a large degree into wealth creation and abuse of the natural world - until, between them, Christians and non-Christians began to rediscover it in their different ways 100 to 150 years ago.
Not sure that the pagans who would no doubt have existed in, for instance, the Middle Ages were any better than their religious equivalents.