More accurately it was not created by the Muslim 'aristocracy', it was created by a mixture of the descendants of Safavi Shia migrants who benefited enormously from the colonial era e.g. Sayyid Mir Jaafar of Najaf allied with the urban Barelvi populations of central india and bengal.
The old...
The mutual antipathy between the Sinhalese and Tamils is several thousand years old e.g. Ram v Ravan. It's not surprising that the Sinhalese chose to convert to Buddhism given how Ravan is depicted in Hindu beliefs.