The designated lineages so far are JN.1.16.1, KP.1.1., KP.2., KR.1, KS.1, KU.2 and KZ.1.1. So 7 different evolutionary paths to arrive at the same advantageous combination, in just a few months.
It's still a bit hard to pick a frontrunner out of that swarm. My best guess is the KP.2.* lineages, descended from JN.1.11.1.
The analysis will become clearer as the Nextclade update has just dropped, providing accurate classification of all the new lineages. It will take me a few days to re-process the data using that update.