Pagan festivals (and traditional, Indigenous, Earth-based festivals around the world) are mostly about the cycles of the year. If you were a pastoralist, you had times when the sheep went up to the high pasture and times when they came down again. If you were a grower of crops, your cycle of festivals revolved around when you planted the crops and harvested them. There were times of plenty and times of hunger. Festivals marked the end of one phase and the beginning of another.
Yule: It’s dark outside, let’s have a fire.
Imbolc: The ewes are pregnant, let’s have a ritual to ensure safe births.
Spring Equinox: we survived the winter, let’s have a party.
Beltane: it’s warm and green outside, let’s party in the woods.
Midsummer: it’s light outside, let’s party late into the night.
Lammas: The crops are in, let’s have a party.
Autumn Equinox: the fruit harvest is in. Cider party!
Samhain: it’s spooky outside, let’s be spooky too.