Christianity was a hard sell back a couple thousand years ago, so it was often simpler to just coopt existing pagan holidays.
That’s a common myth. In most languages (English being an exception), Easter’s name is derived from Passover. Eggs and bunnies are a later development, but through medieval Christian traditions, not pagan fertility connections.
Much is made of the fact that in English, the name “Easter” comes from Ēostre, a pagan goddess. But that’s accepted to have happened because the holiday falls within the month Germanics named after her. Easter isn’t co‐opting Ēostre worship any more than Good Friday co‐opts worship of Frigg.
When I studied ancient Rome, my (secular) education was that Christianity had few adherents at the time, and since the doctrine was very much in flux (many of the books were not even written) and there were social or legal implications to declaring your faith, it was practical to follow the local custom outwardly, while maintaining your faith inwardly.
The most visible is the adoption of Saturnalia (winter solstice) as the time of Jesus' birth. It was the biggest Roman/pagan holiday, and the documentation of his true birthdate was incomplete, so ... Christmas?
The activities of celebration for Saturnalia and Christmas were wildly different (though to be fair, Christmas celebration didn't begin for a few centuries after 0CE, and they did get a bit rowdy in the middle ages!)
The crucifixion is better-documented. That it fell around the time of an existing fertility festival near the vernal equinox might be mere coincidence, I suppose. But rebirth/resurrection/fertility are variations on a theme, so either interpretation can be reasonable.
Additionally (I don't know if this is canon!), Easter is about 40 weeks preceding Christmas. Immaculate conception or not, gestation is still a thing, and the timing is interesting.
In the other half of the world it’s the start of summer.
