As a few someone's posted above thread, he was likely receiving in-state tuition with his TA position. IF that was the case, proving residency earlier was unnecessary. So, like many people, he may have just waited until it was time to renew.
This is incorrect, according to both WA law and WSU rules about tuition BUT, as
@Nova and others have posted, professors have great leeway in calling back their second year students and remediating residency problems if any. He would have lost his second year tuition break if he did have the proof of residency items (usually more than one needed; he could have filed taxes - but the problem is, one typically does not file taxes for 2022 until 2023, and the proof of residency is intended to begin in the first semester).
Which is why it was not smart for BK to alienate his first year supervising professor, who could have used many more things against him, if needed (going into the second year).
While BK did not do all the steps indicated in the program's materials to establish residency in a timely manner, most grad students can still get help from a professor who will write an excuse for them (as opposed to trying to fire them; if the professor sees that some of the rules were ignored AND the student is a social rule breaker, behaviorally, they are not going to urge the Registrar to amend the record - students themselves have no ability beyond providing proof of timely compliance, which if they've missed deadlines, must be rectified by someone with standing to attest to the residency).
He was getting in-state tuition the first year, with the proviso that he do the steps necessary to properly establish residency. One miffed professor who points out that he didn't do it properly could have made sure to point out the error to the Registrar.
You're right about him behaving like many students do (the best ones get things done on time, IMO). But, it costs money to re-register and many students stall it. Campus police are almost invariably lax about these things. And, while WA wants re-registration in-state after 30 days, if one insists that one's legal address is still the parental home, then there is no intent to establish residency and the plates can go unchanged. One then pays taxes in the home state (reporting income from out-of-state while maintaining residency).
This will change FAFSA status as well. I get the feeling that BK didn't really care about such simple rules and, well, he ended up getting booted on other matters.
All imo.