[taneq]

I thought the question was more "why arXiv and not other journals" in which case maybe 'prestigious' Western journal publications just aren't valued as much in China?

[nl]

Almost all ML research is published on arXiv.

In ML (as in most of Comp Sci) conference proceedings (NeurIPS, ICML etc) are where the prestige publishing is.

[HuShifang]

I can't speak specifically to this topical domain, but generally speaking (assuming the research topic isn't politically sensitive) there are professional incentives to do transnational work -- whether it's publishing in Anglophone journals, organizing international conferences, etc. So probably, it's not that foreign journals are valued less. (Probably, in fact, the contrary.)

[lettergram]

Perhaps their papers are disproportionately not accepted to conferences so we see many more on arXiv