The cost of money (that is, interest) is based on two things: the time value of money, which is the concept that an amount of money is worth more now than the same amount of money later (above and beyond inflation); and the default risk, that you may not get back some or all of the money that you lent out.
As the world became more stable over time, the default risk also lessened over time; and there's a good argument that the time value of money also decreased over time, as the quickening of the pace of technological advances meant that lenders could expect more returns over a shorter amount of time. Both factors combined to gradually decrease interest rates in the recent past.
If you believe that we are now in a new era of geopolitical instability, it's reasonable to bet on this long-term trend reversing.