"...Christmas trees came about when Protestant churches decided they were okay, i.e. not too Papist/garish ...

Doesn't make sense! Christmas trees could not have first "come about" in such a context. The statement implies that Christmas trees had been known under "Papist" juristiction, before the Reformation. The Protestant reformers in that neck of the woods apparently rejected the Christmas tree for a period of time, and then had to reconsider and relent.

I suppose the "pagan" impulse to celebrate the Winter Solstice by bringing evergreen foliage into our houses is just too strong to be denied!