From his Tweet, he clearly thinks China is the aggressor here, and that China is withdrawing due to long-term strategic consideration with the US. But it's not as if China and US were best friends back in May/June, 2020 when the whole thing started. Did China forget about this bigger strategic outlook to just to rob India of some negligible amount of inhospitable hills? For what?
China has nothing to gain by provoking India. China's 4 out of 5 strategic frontlines are ocean facing in the east, while the Indian border received the least priority. China never viewed India as an enemy.
On the other hand, India has so much to gain (or at least they think they do) by provoking China:
- By siding with U.S in the trade/tech war, India might get U.S industries relocated to India, which can help India industrialize.
- By winning a border clash India can demonstrate that they can be a valuable member for the U.S led QUAD coalition, which leads to further military co-operation and maybe even military tech-transfers.
- India believed that due to covid, China is weakened, and that political climate in China won't allow a prolonged border standoff; China is likely to capitulate.
China pushed Indian advance back to Finger 4 out of necessity to defend territorial integrity. PLA activities in Galwan Valley and Pangong Lake are based on "底线思维" or "bottom line mentality."
I think, in terms of the bigger picture, most people would agree with his assessment; that the withdraw has to do with long term strategic considerations visa vi the US. But his explanation doesn't really explain why withdraw now? India is in a tight spot currently and China holds all the cards.
Currently, China is arguably in the strongest relative position visa vi India -- In China, Covid is under control, the economy has bounced back; while in India, Covid is still spreading, the economy is in disarray, and farmers are protesting. If China drags this out for another, India would slowly resolve its internal issues, which leads to a stronger position on the negotiating table.
Does this mean India would be disadvantaged in the upcoming negotiation? Once again, China has never viewed India as an enemy. By voluntarily withdrawing now, China once again demonstrate good will and desire for amiable and lasting solution to the border issue.
What if an amiable solution can't be reached? Does this not put China in unfavourable position having to dismantle camps and infrastructure built up to Finger 4? Not really. It took what? Like a few months to build them up, and China can easily build them up again if the situation changes. The same can't be said for the Indian side.
So in conclusion, by withdrawing now, China maximize likely hood of a amiable solution to the border issue with India with no visible disadvantages.