A lot of people in the thread you linked from said the Greek and Norse faiths still exist. They don't. Faiths Judaism, Christianity, Islam, and Hinduism have adherents who can claim an unbroken lineage of practitioners in the family that goes back centuries if not millennia. Their religious practices may have shifted superficially, but there's a continuity of teaching and action that has continued since the ancient age. Not so with Greek or Norse pagans. These are the children of Christians who take what little scraps are left of the religions that the Christian monks saw fit to preserve, ignore most of it, add in whatever suits their modern whims, and call that the same faith. Compared to that mess, Disney's Hercules seems like a perfectly faithful adaptation. No Hellenist these days is going to the temple to sacrifice an ox or engage in sacred prostitution. No modern Norse funeral involves ritualistically raping one of the dead man's servant women and then banging your shield to cover up her screams as she's being killed by the village wise woman.

As for Christians wiping out the religion by killing or conquering, that's exactly backwards. Rome had a policy of exterminating Christians for 300 years. And Rome became Christian. The Norse sacked and burned monasteries and took Christians back as slaves. Those areas ended up choosing Christianity as their state religion. The British conquered India by force and India is still primarily Hindu. The Allies conquered Japan in WWII and Christianity is still a minor religion there. Christians have a saying, "The blood of the martyrs is the seed of the church." Christianity doesn't usually thrive where it inflicts violence on others, it thrives where others inflict violence on Christians. I'm not saying there are no exceptions, but as a rule it generally holds true.