Joseph – “Oberland, i.e. the Chasam Sofer, etc., did not reject Chasidim. They were on very friendly terms and interactions with them even though they never joined the movement.”
It is true that they didn’t put Chasidus into cheirem there at that time, but by then the cheirem already had become history even in Lita, as the Czarist government had legalized Hasidism. That era had passed.
However, that doesn’t mean that Hisnagdus ended. It most definitely continued, just in different forms and ways.
The Chasam Sofer and those who followed him clearly rejected Chasidus (see teshuvos Chasam Sofer), even if they talked to its followers. If you don’t join a movement that wants you to join it, that means that you rejected it.
“And after the war large segments of Oberlander Yidden (i.e. Vien, Dushinsky, etc.) joined the Chasidic movement.”
Dushinsky became semi-Hasidic a long time ago, however, they still retain some Oberlander characteristics.
To say that Vien joined the Hasidic movement after the war is incorrect. R. Yonason Shteif, R. Ezriel Lebovits z”l, led an Ashkenaz kehillah.
The leader afterward, R. Katz, who is Hasidic background, who is still there, broke the condition(s) that they set with him when he was hired, put on a shtreimel and changed the nusach of their Williamsburg congregation to Sfard for the most part. But that is a relatively recent development, like within the last 10-15 years. However, other Vien branches stayed Ashkenaz (with exception of a small Flatbush branch). The changes by R. Katz aroused great controversy. By no means are all Vieners approving of them. Many of the Ashkenaz Vieners have given up on Vien it seems, and joined other kehillos.