But he was right - the Beatles were more popular than Jesus at the time. He didn’t say it in a boastful manner, but to point out the ridiculousness of it. He hated and never understood the fascination with the Beatles.
Nobody understood it (The Tsunami that was Beatlemania), then or now. That mass hysteria filled a spiritual need at that time. Some think America was still vulnerable after the assassination of President Kennedy, and were eager to glom onto anything positive and hopeful. Another example was Tulip-Mania in Holland around 1630. The intrinsic value of average tulip bulbs shot sky high for a while, some got rich, while others lost everything overnight. The tulip was a rarity in that part of the world then, so there was tremendous status value in owning them.