To be more precise, the current areas they've "invaded" are areas that Russian troops have already been in for several years. All that really changed today was that Putin made their presence official.
Not to say that what Putin is doing is "good," but you reap what you sow, and maybe if NATO hadn't lied so much to Russia over the years things would be different. Innocent civilians getting caught in the crossfire has certainly never stopped NATO before.
I'd describe "imposter syndrome" as professional FOMO, where you're worried that all your coworkers think you're an idiot but are too polite to tell you. Sort of like worrying that all your friends think you're a drag but are too nice to tell you.