All honest Biblical scholars (Christian and non Christian) admit and agree that Jesus was not born on Dec. 25. Dec 25 became the consensus date, and logical way, to assimilate the pagan, and Earth based, Winter Solstice gatherings into the Christian religion. The writings in the Bible contradict the creation of Christmas on Dec 25 because of weather. The shepherds and their flocks were not "in the fields", they were in shelter; no one travelled in mid winter (it was too hard) and the manger at night on Dec 25 in Bethlehem was literally freezing. Their whole journey started at another time of the year.
The display in the Capitol of Olympia should show all possibilities of religion and spirituality in our state, including the honesty that Dec 25 and the word Christianity were hijacked to supplant the natural outlook & the Natural Holidays that is our world on Dec 21, the Winter Solstice. Truth, the Earth and her seasons & cycles are way more important than a self described religion. Sometimes the arrogance of religions is maddening.
According to most sensible researchers, the date of Jesus' birth is September 29, 5 BCE.
Is Jesus "the reason for the season"? Sure, with qualifications, because history, spirituality and common sense show us that Jesus is just "one of the reasons for the season". In America, the religion of Santa Claus is stronger.