IIRC, United blinked first on their NRT-BKK service. So DL was the only remaining US carrier serving BKK at that point, they got all the (remaining) passengers and corporate traffic, and it still wasn't enough to save the route

USA-MNL definitely has a revenue purpose in DL's network, although the fact that it remains on DL metal via ICN has more to do with the Korea - Philippines bilateral agreement. KE can't add anymore flights (or maybe seats) on their metal, but DL is able to do so. Now, with depressed loads everywhere, you wonder if KE can absorb all of the traffic within their footprint thus rendering DL's service unnecessary. I hope I'm wrong & DL can maintain that service.