The DSA and other socialist groups will have some opportunities to show their governing chops. I think if their main interest is "revolution" they will be voted out in short order. If they find ways to improve the lives of their constituents, they will be rewarded at the polls. It is pretty simple.
I've known DSA peeps for a long time. They come in two stripes. The pragmatists and the revolutionaries. Soon enough we'll see which kind Buffalo's new mayor is.
Btw the revolutionary and pragmatic can be combined in one person. Bernie Sanders was fairly pragmatic as mayor of Burlington. For most of his Senate career, he was in revolutionary mode, an angry voice in the wilderness. He has become more of a pragmatic again in recent years, willing to negotiate for half a loaf.
With respect to Buffalo, there is nothing that precludes the Republican Party from running a serious candidate. In Buffalo or any other major city. Many blue states and cities have benefited from talented Republicans winning office. Like the DSA, however, it seems that Republicans these days come in two stripes, the pragmatists and the revolutionaries. The former seem to be in increasingly short supply. There is one major difference. The DSA is willing to do the hard work of organizing and trying to persuade voters. I don't see much in the way of similar effort on the part of Republicans. Certainly not in our major cities. It's a shame.