That's generalizing. Many immigrants from places other than India or China immigrate and don't find academic success at the same level. Why are these immigrants doing better than others. Part of it is cultural (placing social behind academics) and the negative pressure of lower marks. Part must be selection bias (the best and brightest come because of the hurdles they need to overcome to even get accepted).
We don't see these rates with latin American immigrants, African, Middle eastern or europeans. Part of that is opportunity locally (the best and brightest don't leave when opportunities exist locally).
You see so much more cheating with the first immigration group. Is that because learning isn't as important as grades? Why don't locals cheat more? Too much effort?
Has the false promises of education (education will fix all) registered as more apparent in the west and many are choosing to skip or is the system designed for other outcomes.