Unfortunately the links you posted don't provide any evidence or suggestion that RT or Sputnik promoted these stories.
It does seem like there are a fair bit of analysts in United States intelligence (Clint Watts being on that side of the fence, essentially) who strongly believe that RT or Sputnik are less media sources, and are instead funnels of disinformation propaganda designed to destabilize the United States government. Whatever your personal opinion of these media sources are, in this light, Twitter's action here is hardly surprising.