Could it have been if Donetsk becomes independent destroying the plant would mean major industrial loss?
Well, a couple of points support that, the breakaway Oblasts are a very large part of the Industrial, Manufacturing, Mining Industries in Ukraine, and the Workers (many Russian Speaking) are skilled and oriented to heavy industry, mining, and infrastructure.
However, Ukraine has been shelling said industries and workers for about eight years, so much damage has been done.
Russia will have to rebuild all of that alone.
Would they opt to protect Azovastal Steel now, or write it off for future reconstruction?
I frankly, don't know the answer.