>Russia remains bogged down in Ukraine. But Putin does not need another invasion on the scale of Ukraine to challenge NATO. He can move up an escalation ladder: sabotage, cyberattacks, assassination plots, drone or missile attacks — and then a limited military operation designed to test whether NATO still means what it says.

So Russia is too weak to conquer Ukraine but wants to risk other countries joining hot war? What for? Get bogged down even more?

TL;DR: Because Russia is ramping up hybrid/unconventional attacks, and Belarus is training for an attack on the Baltics. Russia and Belarus are being aggressively hostile; if you want peace, prepare for war.