Why do companies delete job postings?

Very recently had an interview at a place. Felt pretty confident about it and sent individualized thank you emails to the many people I met during the process at the company. The job posting disappeared about a day later.

Is it assumed I am one of the final candidates? Or an offer was already given/accepted by another? I was told I would hear back from them within a week or so. I know their application pool isn't huge as some websites show how many applied to a job.

Also a bit of a random side-thought: this was easily one of the best experiences I had with HR. Super responsive and helpful for my inquiries.

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