The reason for their demise is precisely because they invested into long-maturity bonds, ignoring the fact that customers may want, someday, to get their money back in the short-term.

They chose these long-maturity bonds is because they were offering higher yields.

Now of course, seen from today, these yields are very small, but when they invested, it was at a time we were talking about zero or negative yields in many currencies.

It's like they risked it all, to get 2%.

cf. https://twitter.com/debarghya_das/status/1634021769656016896