Why is taking so long after the "final interview"?

I did my final interview yesterday, which was the fifth round. I've been told that I am the leading/top candidate. It's been only a day, but I haven't heard back yet. It made me curious/wonder how much more time the company needs after five rounds of interviews and case studies to make a decision. What's blocking them from making a prompt and swift decision? Any insights? This is not a rant, and I am genuinely curious.

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