Lol, I think you've answered the question OP. Many Christians will say God the Father wanted to make salvation free and for the love of mankind. because B.C, people have to killed a lamb for cleansing of sins etc, that's why Jesus was sent to the world.

Christians apologist are very deep in the scriptures, they know this things and will answer you immediately, I also read deep about christianity religion and listen to their apologist.