Why would my now engaged ex who I didn’t speak to since 2018 message me out of nowhere?

I asked him how his love life was and he told me he’s engaged.. is it not odd to randomly message me we only dated for two months maybe three. In 2018. it went really sour and he blocked me but we became civil months later after I messaged him on another account.
but after a few months we blocked one another again and never spoken again for three years or so till …… yesterday, when he randomly followed me on Instagram and messaged me asking how I am
Why would my now engaged ex who I didn’t speak to since 2018 message me out of nowhere?
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