It was a while ago, but here is what I remember off the top of my head… as the Wemos & Node MCU already apply an internal voltage divider that allows up to 3.2v input on the 1v limited ADC (in theory 3.3v is allowable)
https://wiki.wemos.cc/_media/products:d1:sch_d1_mini_v3.0.0.pdf
Adding in the 180K Ohm resistor just worked with the internal voltage divider (via Ohms Law) to increase the allowable input value to 5v.
Internal Voltage Divider calculation…
Internal voltage divider with additional resistor…
Additional resistor brings one leg of the divider to 400K… maintaining the ADC limit of 1v
