The Chinese side of the story is heavily censored and only has official reported numbers (likely tampered with, knowing China) and some propaganda pieces, but this is very much a Chinese national emergency as well. The Guardian’s latest reporting claimed that the Chinese officials reported 16 deaths and 546 missing, while Nepal’s numbers are 675 deaths and 2,498 missing

Maybe there are ulterior motives, but I think given the extent of the disaster, it is much more likely that China treated it as a top-priority national emergency, so might as well help out the neighbors with any extra manpower as well