You may be right about this particular instance. Do you have evidence the factories will still be owned by China? From what I can tell they are using Foxconn so that is not the case.

Samsung also exited from China as will many more companies. Corporations have been exiting China for awhile now because manufacturing prices are lower elsewhere. They also get sweet deals from governments doing this and in a lot of ways it is predatory in nature as they will leave Vietnam if it is more profitable somewhere else in the future.