They weren't making money on NRT-LAX. With about four daily nonstops ICN-LAX-vv, no one going through wanted to make the stop, so it didn't really function like a tag route (it wasn't like pinning EZE-SCL onto AMS-EZE or SIN-DPS onto AMS-SIN, where a goodly number of pax are flying both segments). So that meant the route was really an independent NRT-LAX route that competed against all the others flying that route and indirectly competed against HND-LAX. Just too much competition, most importantly from home carriers JL, NH, UA, AA, and DL.
KE 001/002 now serves HNL. Reportedly the slot restrictions at NRT meant that the flight had to go TPAC, not turn back to ICN as another NRT-ICN frequency. So they're giving HNL a go. No word on how it's doing. But a recent flight on the NRT-ICN segment didn't look like it had impressive loads. F and J were mostly non-revs.