According to Osho, the Jain stream became loveless because, after ages of excess in the name of love and God, Mahavira corrected course toward meditation and austerity, placing love as the fruit, not the practice. Later generations clung to doctrine and zealously cut attachment, inadvertently discarding love; without walking to realization, love never manifested, so the tradition dried.
To avoid fake ‘love’ and God-talk, people leaned so hard into strict meditation that they threw out real love and, stuck in rules, never reached where true love naturally appears.