I don't think Yandex DCs are used directly for military purposes much. It's more about harming Russian economy in general, including its highly prided digital infrastructure
I don't have specific information about Yandex but don't forget how heavily involved Amazon were with things like: https://www.nytimes.com/2022/12/19/world/europe/ukraine-cybe... it wouldn't be a huge stretch to suggest that a lot of cloud hosting providers are neck deep in national security.
Ukraine has a very targeted response but notably tries to minimise civilian casualties
Also Yandex is a large cloud provider, they host a lot of government-connected companies.