Didn't the Buddha also teach love?
Yes: the Discourse on Love (Metta Sutta) is beautiful, and Christians can honour it. The difference is where love comes from. In the Bible, love starts with God, who loved us first and gave his Son.
The Metta Sutta asks for a boundless heart toward all beings, like a mother protecting her only child. Jesus asked for love even of enemies. But the Bible goes further: God is love, and he showed it not by a wish for all beings but by an act in history, sending his Son for sinners.
Even as a mother would protect with her life her child, her only child, so too for all creatures unfold a boundless heart.
Sutta Nipata 1.8:7.1-7.4, The Discourse on Love (tr. Bhikkhu Sujato) · context
44But I tell you, love your enemies, bless those who curse you, do good to those who hate you, and pray for those who mistreat you and persecute you,
Matthew 5:44 (WEB) · context
9By this God’s love was revealed in us, that God has sent his only born Son into the world that we might live through him. 10In this is love, not that we loved God, but that he loved us, and sent his Son as the atoning sacrifice for our sins.
1 John 4:9-10 (WEB) · context
19We love him, because he first loved us.
1 John 4:19 (WEB) · context