> I wonder how developers of computers came to idea to use binary numbers?Essentially a logical consequence of electronics and the equipment they were working with at the time.
That 0 and 1 are not pure zero-volts and 5-voltsⁱ. There is a lower range that will definitely be ready as 0 and an upper range that will be read as 1, and hopefully the signal doesn't spend long between them. Also switching isn't absolutely instant, switches bounceʲ, debouncing methods smooth that but drag out the time to transition from 0->1 or 1->0.
All of this is try for multi-level electronics but even more so, making it easier and more reliable to work in binary than 3, 4, or more levels per bit.
Ternary (base 3) computers did exist, some using -1/0/+1ʰ and some using 0/1/2, and multi-level logic is used for some storage methods today, so binary isn't the be-all and end-all it is just most usually the most reliable & convenient tool for the job.
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[i] or 3.3 or whatever other logic levels you are using
[j] a lot less of a problem with microscopic transistors but think back to old chunky relays & tubes
[h] not sure if that is just notation or there were negative voltages involved - I last read about these things properly at Uni ~2.5 decades ago