The invasion was so urgently cobbled together that many Russian forces were using amateur radios to communicate, they had no support infrastructure in place, or even fuel for the vehicles containing that infrastructure. Numerous soldiers were captured carrying off the shelf radios (literally think eBay), and there are various reports they rely on the mobile phone network to coordinate with central command. There was allegedly also a recent misappropriation scandal where cheap Chinese communications gear was purchased and relabelled before being sold to the Russian military, suggesting they might not even have real equipment to give to their troops.

Separately, having coordination done via "www.google.com" DNS & SSL ClientHello makes it all but impossible to block without disconnecting the Internet for the entire country, at a time when access to information within the country is more essential than ever.

Everything about this sadly makes sense