Nvidia has things like the A series for this sort of stuff, and at their level of use they'll be buying at a distributor or direct from manufacturer level depending on size.
Some small places will want 4090s and things though, and then yeah maybe they'll buy from stores and that but I doubt that'll be enough to kick demand up and cause prices like the crypto boom.
To be fair to Russia I think they envisioned a complete rolling of Ukraine, if they had known that it in fact would be a 2 year+ long war leaving 150k of their men dead and most of the equipment depleted they'd have maybe not done it.