Its not actually new, The companions would praise the Mawlid, now we have an occasion called Mawlid. Allah Ta’ala says let them show joyous celebration some among us and the sahaba showed joyous celebration.
Mawlid and its celebration is not a Bidah, the occasion called Mawlid is a Bidah Hasana [good innovation]. So the companions never had an occasion called Mawlid, or Milad but the Mawlid was commemorated
Your elders are blessed to have had RasoolAllah SallAllahu Alaihi wa Ahlihi wa Sallam in their hearts