I am currently watching Mahabharat on Hotstar online streaming service and I am very much loving it. I have heard this coronation song first during Bhishm’s coronation, then during Pandu’s coronation and also during Yudhishthir’s in later episodes. I searched on google on who wrote this but couldn’t find it.
No one wrote it. The mantra mentioned is actually a mantra used for ‘Mantra Puṣpāñjali’ or offering flowers to a god after a puja or Aarti.
This mantra is from the Taittirīya Ārāṇyaka (Kṛṣṇa Yajurveda) Prapāṭhaka 1 Anuvāka 31 Mantra 6:
राजाधिराजाय प्रसह्यसाहिने। नमो वैश्रवणाय कुर्महे। स मे कामान्कामकामाय मह्यम्। कामेश्वरो वैश्रवणो ददातु। कुबेराय वैश्रवणाय। महाराजाय नमः।
rājādhirājāya prasahyasāhine। namo vaiśravaṇāya kurmahe। sa me kāmānkāmakāmāya mahyam। kāmeśvaro vaiśravaṇo dadātu। kuberāya vaiśravaṇāya। mahārājāya namaḥ।
Meaning (from Kamakoti): King of kings, we praise thee,Who is the giver of all victories,Who is the fulfiller of all desires, Please bless me with wealth,To fulfill all our desires,Oh, Kubera, we praise thee, Salutations to the king of kings.