The language of the past colonizers are usually spoken in their former colonies. Like French is still spoken in parts of Canada and how Spanish is still spoken in parts of the US that were previously parts of the Spanish Empire or Mexico. But I know that French isn't spoken in Louisiana because of active discouragement of it in the 20th century. But what is the reason behind Russian not being spoken as much in Alaska? Is it similar to that of Lousiana French?
You may find this answer by /u/The_Alaskan to be helpful. While the issue of language is not addressed per se, it is noted that there were never many ethnic Russians in Alaska and most of them left after the treaty.