1. Selection bias. There's a lot of stuff in the Bible that is total gibberish to modern ears.
2. Inversed cause and effect. Even if you aren't Christian, there's a good chance that the morals you were taught as a child are influenced by it. The Christian Bible is literally the world's best selling book.
Going further it's in fact the very foundation of the morality of western civilization. It's little wonder why it's constantly under attack and diminished.
Western civilization existed long before the bible (the Greeks) and the predominant culture spread throughout western civilization (Roman) was non-Christian long before it was Christian.
2. Inversed cause and effect. Even if you aren't Christian, there's a good chance that the morals you were taught as a child are influenced by it. The Christian Bible is literally the world's best selling book.