Why should Putin be afraid of the West? Everybody knows that since the 90s, the West has been busy disarrming, even as they get involved in stupid wars like Bosnia, Kosovo, as well as nationbuilding projects in Afghanistan & Iraq. If he marches troops into even a NATO member, say Latvia, NATO will be exposed for being as feckless as it is.
Real reason is that Russia has been a weakening power, and incurring huge casualties in Afghanistan and Chechnya did nothing for their confidence. If they lose thousands in a war w/ Ukraine, they'd be seriously embarrassed, and any other internal secession movements there, like Tatarstan, could erupt. Which is why they are trying to subvert Donbass into becoming a part of Russia.