When you actually stop to think about the required core skills of good snipers, you would see that that list of requirements actually favours the Chinese in many ways.
When you are going past 600-800m (depending on the weapon), sniping becomes a math problem. Calculating bullet drop, windage, time to target etc comes down to remembering tables. Experience will help someone to be able to guess it, but that is far less reliable than knowing the exact, scientifically tested and proven numbers.
It is not uncommon for even top snipers to whip out their ballistic tables to consult when taking a really long shot when they have time.
Considering all Chinese middle school kids learn the Pi times table, I would almost expect their snipers to have all the ballistic tables committed to heart.
That means in the time pressured environment of these sniping competitions, the Chinese snipers would be aiming their shots based on actual ballistic table figures, whereas the vast majority of others will be going by experience of 'feeling'. Little wonder who would have the upper hand in such circumstances.
The Chinese snipers are also far more dedicated in developing their 'hard skills'. Part of their standard sniper training is for their snipers to assume sniping positions, and hold it steady enough that an empty shell casing placed on the tip of the barrel of the sniper rifle will not drop off for 'half a day' (although that also means 'ages' colloquially in Chinese, so might not be meant to be taken literally, but the minimum amount of time possible is 30 minutes, but probably over an hour).
That is just standard training for the guys using Type 88s, what many in the west insist on calling DSM instead of 'snipers'.
I think the main reason the PLA snipers 'lagged by 20 years' when they first entered the competition was because up to that point the PLA paid little attention to sniping beyond 600-800m. Possibly because up until recently, their only sniper weapons were SDVs and Type 88s that lacked the range and accuracy to be useful beyond those ranges.
But once they woke up to the advantages of being able to snipe up to 2km, and started to invest in R&D and purchases of true sniper class weapons as well as doing research on long range sniping, is it any wonder they would do well when they brought the work ethic and dedication that they used in training with the Type 88 to training with R700 and newer indigenous Chinese sniper rifles?