If inciting a riot in the Capitol during the certification of election results isn't treason, then I don't know what is. I'm not sure that Pelosi wanted to open that particular Pandora's Box. Anything resembling governance is hard enough, as things stand. That road would have guaranteed its impossibility. There's no getting to the two-thirds standard necessary for explusion, so we'd have ended up with a bunch of members wearing Obama's facial expression glaring at a bunch of members wearing Putin's facial expression across the aisle.
I think leaving the box closed is a tactical error that just kicks the can down the road, and will be more costly in the end, but I'll concede that Pelosi might have been right. It's certainly one way of looking at things. To quote Robin Williams in an old film, she is riding a psychotic horse through a burning stable. Just hanging on for dear life is one way of dealing with that situation.
It is incomprehensible to me that in two decades we went from hanging chads to "Stop the Steal" and a literal riot. It's like half the country turned into Gen. Jack D. Ripper, only they're not on about fluoridation specifically.