I think Instagram wasn't annotating their pages with either OpenGraph metadata or Twitter card metadata, and so you got a bland link vs a rich preview.

It seems like Instagram _were_ publishing og:image tags at one point, but then removed it. See, for example, this 2019 reddit post [1].

Instagram then announced a change to this policy in December of 2021 [2] and now annotates with og:image again.

[1]: https://www.reddit.com/r/Instagram/comments/dn2wsw/saving_an...

[2]: https://about.instagram.com/blog/announcements/introducing-b...

https://techcrunch.com/2012/12/05/kevin-systrom-on-pulling-t...