Good question. I guess it's easier and more joyful to celebrate something happy and good than to celebrate something bad and sad.
Then there's the issue of extending a salutation to someone in commemoration of this hallowed event. Saying "Happy Good Friday!" seems to be doing it all wrong.
Good used to be a synonym for holy and pious. About as close to you will otherwise find it still in usage is when people refer to a ship in reverence as "the good ship (insert name)".
Correct. "Good" came from "God." My Father, who was Jewish, didn't believe in a literal God. He would always say he believed in a "Goodness." And, that was holy. And, it is true as well as there is a literal Godhead, The Father, Son and Holy Ghost. Also, the Atonement took on 3 parts. The actual taking on the sins of the repentant and baptized in the Garden of Gethsemane, the crucifixion and the resurrection. All for the benefit of the Father's glory and his Children.
The people who nailed Jesus to the cross were Roman Soldiers; from Vatican City. The Pope killed Jesus by proxy, and then used the method he killed Jesus as a symbol of his religion when making the religion a couple of centuries later. No doubt Jesus' execution was on record in Rome/Vatican City, and they just dug out the case of Jesus of Nazareth from their archives and made him a martyr. It's a religion of lies designed to damn us against our natural lives and to submit to their power claiming it to be higher.