You’ve asked what I understand as two separate questions. Your first question is one of history to me because I think that way. Your second question is different. I’ll answer the second one for now. The essence of Christianity is love. First, God is love. 1 John 4:8 Out of love he created us (also for his glory). We have been taught to address him in prayer as Our Father, and we are his adopted children, definitely a love relationship. We are justified because of the great love he has for us, and has shown so clearly in his Son. Our happiness will be found in loving God (loving Jesus), and being with him in heaven. Paul describes the relationship of Christ with the Church as like a husband and a wife. Eph 5:25 + It is thus about love. Without love, we are nothing. 1 Cor 13:2 Christ gave two summary-like commands, to love God and to love our neighbor as ourselves. Furthermore, he gave us a new command, and that was to love one another as he loved us, and as you know, he died for us out of love. We are called to clothe ourselves in love. Col 3:14 Even suffering is about love, like the suffering of Jesus on the cross or like how God chastises his children whom he loves. Heb 12:6The internal life of God is love, and for men, their past, present, and future are about love.
Phil 2:4-5 Let each of you look not to your own interests, but to the interests of others. Let the same mind be in you that was in Christ Jesus,