You can't even spell their name, but you want us to believe that unlike the authorities in the country where they operate, who have access to all their financial records, you're an authority on the solvency of co-operatives running Swiss supermarkets ?
Migros isn't going to go bankrupt. If for some reason the conditions in their marketplace made it tough to continue to spend 1% of revenue on community projects they could go to their (millions of) members and seek authority to discontinue this practice or put it on hold for a period. But in reality even with foreign for-profit discount supermarkets entering the Swiss market there seems no likelihood of a serious threat to Migros. It is well-loved by locals.
Your estimation would be wrong even for a for-profit corporation running supermarkets. A well run supermarket can easily clear 1% profit, which means if they gave 1% of revenue away they'd be close to break even. But supermarket chains have routinely operated with as much as 1-2% losses without being in danger of creditors seeking administration, let alone bankruptcy. IIRC Aldi, in my country, went from -1% to +1.5% in twelve months under new management and even in financial papers it was never front page news.