I wonder if it has anything to do with the recent identification of Tammie Liles, which confirmed that he did commit murders outside of King County. As a reminder, he agreed to a plea deal that required him to confess and lead investigators to more victims in exchange for the prosecutor not seeking the death penalty. This plea deal only covered crimes committed within King County. Hence he never confessed to the murder of Angela Girdner, which he has always been suspected of, because she was abducted from Oregon.
Angela’s remains were found with some unidentified bones in Oregon (recently proven to be Tammie Liles). Here’s why that’s important — he confessed to killing Tammie, who was abducted from Seattle, years ago and led investigators to SOME of her remains in King County. He would sometimes revisit his victims and try to confuse investigators by taking some of the remaining bones and leaving them at another dump site, which is exactly what he did with some of Tammie’s bones when he left some of them in Oregon next to Angela. When those bones were identified this year as belonging to Tammie, it provided evidence that he did in fact also kill Angela, which he had previously denied.
This means that prosecutors in Oregon COULD choose to pursue the death penalty now. This could also mean that Oregon investigators could now be looking into cases that have yet to be connected to him.
Long story short, I have no idea what any of this has to do with him being transported back to King County, but LE has the power to reopen things since they can now officially tie him to crimes in another state. It certainly appears that something is going on behind the scenes.