Businesses and Government also can be temporary suppliers. It should be no surprise that as interest rates rise suppliers are more willing to supply funds. This is partially the result of a higher propensity to save in these countries. The real rate if what matters. Thus if inflation is higher than expected, the lenders lose.
Budget deficits increase demand for loanable funds and hence lead to higher interest rates.
Foreign flows of funds can influence interest rates. For example, Japan recession led to lower Japanese rates, thus investors supplied funds to the US rather than Japan. Of course this drove down US rates. Looking at the 1900s, it can be shown that interest rates have become more volatile in the past 20 years. This is in part due to increased global flows as well as the end of fixed exchange rates.