It helps a lot to have a small countryMaybe, or a big but dictatorial country like China.
an ethnically homogenous population
Care to elaborate? Would you consider countries such as Switzerland, Canada, Taiwan, and Singapore ethnically homogeneous?
extremely low corruption, high tax morale, and high public trust of government offices and institutions.
Chicken and egg problem - High tax compliance and trust in government come from having a reasonable tax rate from which you get a lot of effective government services. Low corruption is a pre-requisite for trust in government institutions.
I bet what also helps is not having a culture of cousin marriage, that seems to create a culture where is much more difficult to have any kind of trust with people outside of your clan.
I think the modern well functioning democracy is to a very large degree a result of complex game theory.
You don't have to look back much more the 2 centuries, to see thousands of years of European history that's full of corruption, lawlessness, crushing tax rates, all the typical modern day 3rd world problems and then some.
If just being Swedish led to modern Sweden, Swedish history would be a lot less interesting. For one, it would almost certainly be entirely Viking free.