From the legal point there is no insurance claim payment if it would be found that it was an act of self-sabotage or part of a war like conflict = 2 typical exclusion clauses.
This rather excludes Russia and Nordstream shareholders from self-sabotage point of view, see here.
There would also be no payments would the act be part of a war - Ukraine did it, but there is little for Ukraine to gain as there was no gas flowing, that culd upset Germany, France and Dutch.
If Russia is found to be involved in the Nord Stream 1 damages, it could be considered an act of war, something that is typically excluded by insurance, here. Russian state assets could be used for damages. So this did not happen.
NOTE:
Is this THE reason why there is not release which state was involved???
Likely so!