Why is opposition from Belarus so intense? Because they want to seize the wealth of Belarusians.

 "EU sanctions on potassium fertilizers would be a valuable gift to Russia. It is particularly interested in finding options with Belaruskalij on its own terms. One possible option is for Belaruskalij, which controls 21% of the global potassium fertilizer market, to be paired with Russia's "Uralkali". Their combined share of the global potassium fertilizer market would be around 40%, which could dictate conditions. It is also possible that Uralkali would buy the Belarusian potassium fertilizer plant with strong Russian interests, so  that there will be nothing left for opposition to manage, because the most valuable assets will be deposited in the pockets of the Russian oligarchs. 

There are also some unpleasant moments in the Belaruskalij plant, which is in the basket of EU sanctions. Allegedly, EU sanctions, specifically on Belaruskalij's production, benefit German fertilizer producers by eliminating one of their main competitors. Sanctions will also damage the global market for potassium fertilizers, which is in short supply. EU sanctions on Belaruskalij plant's output could further push up potassium fertilizer prices."