Is there any actual evidence of this? I’ve heard that claim, but it seems like most trump voters were Republicans, not democrats who got duped by bots.

To be fair, that "certain" fact is wildly disputed. It's like the political equivalent of "reefer madness" in that it's easy to throw around, yet hard to quantify or present as a valid case for/against.

I mean, look at the absolute circus a controversial point such as "how did Trump get elected" has caused in the US and even world-wide. We're nearing the next election and I would argue it's still no where near resolved. In fact, I'd argue it's caused a bigger divide than anything else precisely because it's so un-pinnable to being either true/false or good/bad.