You don’t have a point considering Christianity came about through the belief of Christ.
What grade are you in? Christianity is Abrahamic because God fulfilled Jewish prophecy through Christ, who was Jewish. Christians adopt all that came before Christ as the word of God, as well as the Gospel.
Islam made up a religion and invented a claim 700 years later that Abraham was the ancestor of Arabs. No one had ever suggested any such thing prior to him.
Identity theft does not make you into the person you pretend to be. Islam is not Abrahamic, it is only Muhammadan.