There's always been white supremacists and racism in Oregon (especially in eastern Oregon) But the idea that Oregon was founded as a "white utopia" is actually kinda ahistorical, or at the very least a gross (and somewhat irresponsible) misrepresentation of what lead to the official banning of non white homesteaders. And as far as I can tell the "white utopia" thing really only became a popular narrative immediately before and after Bernie Sanders won Oregon's closed primary and people wrote a lot of articles pushing the idea.
A lot of settlers in Oregon were people fleeing the civil war. Usually out of self preservation. But many also left due to apathy, or because they were racist white supremacists and wanted to go live out in the middle of nowhere, where there were less black people. So black people in general had a hard time actually claiming homesteads, since people would just kinda ignore their claims a lot of the time.
But Oregon wasn't special in that fact at all. California, Idaho, Nevada, Montana, etc, were all founded on just about as much informal racist policy and fear of the civil war spilling into the west. And black people seem to have had just as much trouble moving to the rest of the west and claiming a homestead.
Where Oregon territory was special though is that they at one point officially announced that non whites were not welcome to settle there. It had been an unofficial policy pretty much everywhere in the west, but because of an incident in Eastern Oregon the distant state government was convinced making it official policy was necessary to prevent imminent race violence.
Out in far eastern Oregon in 1844 there was a conflict between a native american man and two free black men over ownership of a horse. A brawl broke out, and it left three people who were involved dead.
The white settlers started causing a panic and ranting and raving to the distant central government that an influx of black people could escalate tensions with native Americans and cause imminent race violence and uprisings against both white and black people. And as such, the government should ban black people from settling to prevent a small scale race war. For the physical safety of everyone, black, white, or native american, you see.
The state was convinced by the argument and the panic, and passed a law banning blacks from settling.
It was never actually enforced, and some local communities intentionally subverted it, but it still had the desired effect of letting black people know they were not welcome and it discouraged most black settlers from moving there instead of to California, or wherever. And so the pacific northwest has had less black people in it than the rest of the west ever since then.
So it was never really founded as a "white utopia". It was more like a typically racist western state who had an incident make them more explicitly racist. But under the guise of it being a humanitarian and "progressive" decision. Not as white supremacy. Which I think is a very important distinction to point out. Not that there weren't white supremacists who would have loved for it to have actually been founded as a white utopia, mind you.
Still though, the progressives and the State quite obviously feel guilty about it (I mean as they should) since they eventually reversed and denounced the decision, and have fairly consistently and explicitly tried to combat systemic racism for almost 100 years now. Usually by actually introducing black people into positions of trust or authority. For example, Portland had the first black teacher of an integrated school in the U.S. because the State and voters made sure that he was were hired. Stuff like that seems to have helped a little bit with the skewed demographic, but it's still a ways from being fixed.