After two years together how can an ex just jump into a new relationship within weeks of the breakup?

It ended mostly amicably despite caring a lot about each other (so I thought). How can people move on so quickly?

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+1 y
Thanks for all of the opinions. To all of those who are saying he’d already checked out before we broke up (I think you’re probably right) but then why would he be nicer to me afterwards and want to meet up with me again as soon as I went no contact?
After two years together how can an ex just jump into a new relationship within weeks of the breakup?
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