Cheap for a reason - and these reasons already existed before the war.
If you have ever been to Ukraine you should know that the country has zero opportunities, except for agricultural. "Brain drain" is excessive, meaning that every person who can is trying his/her luck outside the country (ironically, many in Russia).
Just because something is cheap does not mean that there are opportunities.
Aside from that, once this conflict ends you would own land/assets in a part of the world which certainly will not favour any western investments. It won't︀ take long till your land or whatever assets will be seized.
Investing behind ideological front︁ lines is a bad idea: You do not have any legal recourse in the country︂ of your investment. Furthermore, sympathies in your home country will also be quite limited because︃ you invested with the enemy!