The ruble is stable because no one uses it. Persistent devaluation and shortages of cash so undermined confidence in the ruble that private citizens and corporations alike abandoned it. Citizens abandoned the ruble because devaluations wipe out ruble savings. But, even stuffed with dollars, socks don't get counted in Russian money supply. For that matter, neither do corporate accounts receivable.
Devaluations also wipe out the cash component of working capital.
Veksel' are corporate IOUs- fungible credit instruments Russian industry uses to discount its receivables. In most capitalist economies, commercial banks discount corporate receivables. In Russia, however, banks don't make loans, so accounts receivable rarely show up as demand deposits in commercial banks. Or, obviously, in the money supply. No wonder Russian money supply is so tight.