Ever heard the phrase "don't try to catch a falling knife"? We don't know how far this crisis will go. And we've only just started on the path of serious sanctions.
The risk of the companies disappearing may indeed be low.
One historical fact does come to mind: the St. Petersburg stock exchange reopened in 1917 (after being closed for world war 1), then closed two months later because of the Russian Revolution. It did not reopen and shareholders of Russian stocks lost everything.
I don't see something like that happening today. But what if Russia confiscates the shares of foreign shareholders?
But will it go lower? Will it ever go back up higher? Will the company you invest in go bankrupt, or its factories get destroyed (intentionally or accidentally)?
I mean if you have the money and confidence by all means, take the gamble, but keep in mind it's a gamble. Don't sell your house, don't spend your reserves, don't bet everything on one horse.
For Russian one - Putin controls all of the companies in a way. Shareholders have no say. This is reflected by the markets. Market cap of the exchange was 700b, largest US tech companies are larger on their own.
For Ukrainian one - the country might not exist in a few weeks in the current state.
If you want to play on the effects of the conflict, either buying or shorting the ruble is the best way to go.