If out of proportion in scale, back in 2000, Nader voters going for Gore would have decided the nation for everyone. Ultimately the choices of a few hundred people overcame over half a million votes going the other way. The very small number of Stein voters in a certain place can decide the output. I don't fault them for 2000, even if I disagree with them, because I don't think folks could have reasonably foreseen the warmongering that was to come.
If out of proportion in severity, between November 2020 and January 2021, you had several attempts to undermine the election, and that was with very little planning/prep work. You had trying to get the states to "find enough votes", you had fake electors, trying to get the VP to unilaterally refuse the election, inciting a crowd to storm the proceedings. In the aftermath you have certain people planning their whole political careers on promising to guarantee the elections for GOP, speculation that Vance was picked carefully as someone willing to do what Pence wouldn't, and a whole carefully constructed plan to start getting things ready for 2028 election the moment 2025 starts, if they can. You have a supreme court that ruled that a president may be considered immune for crimes, unless of course the supreme court decides it's not an "official act", reserving the ability to selectively enforce law on the president themselves.
With respect to Russian influence, this is specifically a Stein situation and plenty of evidence to support that Stein is being supported by and manipulated by Russia. It makes sense too, as Trump has shown himself to be awfully susceptible to Putin's manipulation, so taking advantage of a naive Stein to foil the votes of naive voters in favor of Trump is a plain strategic path for them.
Yes, we can talk about her platform, particularly about her wish to dissolve NATO and stop support of Ukraine, but other parts of her platform are difficult to explain the nuance of the problems. Like "dump money on third world nations", which sounds the decent thing to do, but historically trashes any semblance of local economy and frequently reinforces warlords instead of the people.