Many girls and women tie a rakhi to Lord Krishna on Raksha Bandhan. Some even tie a rakhi to the Lord before tying a rakhi to their brothers. This is because Shri Krishna is the supreme Lord of compassion, protection, and love. His devotees see Krishna as their friend or sibling. Hence, many women also think of him as a brother and tie a rakhi to him.
Women also tie rakhi to Lord Krishna because he saved Draupadi from public humiliation and protected her sanctity. Similarly, women believe that Lord Krishna will also protect them from negative energies and evil eyes when they tie rakhi to him.