Contained within it's borders. You mean like constrained from territorial expansion and annexation of neighbouring territory? Yes. Just as all the European countries are contained within their borders.
Being constrained within your borders should be the default for everyone. The fact that Moscow has a president that doesn't think that way is exactly the problem NATO was created to deal with.
I'm a realist, I know there are cases when military interventions are necessary. Preventing genocide in Kosovo, kicking the Iraqi army out of Kuwait. There can be messy situations where the right course of action isn't clear, but Ukraine is not one of those. Flat out annexing large swathes of neighbouring countries is precisely the problem NATO was created to counter. It turns out for very, very good reason.
That's not where I would put the emphasis. Though there was some courting, the anti-Russian sentiment in these countries was genuine.
Russia shares its borders with 14 other nations. What happened is that, one by one, many of these joined, or became partner to, an alliance which views Russia as something to be contained. Russian leaders may not have been worried at first, but that changed later.