Why does electron configuration in the periodic table is different when you follow the aufbau principle?
As a general rule, full electron shells are more stable than unfilled shells. In silver, promoting an electron from the 5s to the 4d shell completes the d orbital, which increases the stability of the 4d shell more than it destabilizes the 5s shell.
This is also explained here:

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=21&amp;t=2807