It is much, much easier for Estonians to afford cars than it was a decade ago. Without making transit free, car traffic easily could have gone up even more.
The lesson for planners and government here is clear: combine free transit with measures to make it massively more incovenient and expensive to own a private automobile.
How did you make a jump to that conclusion? Correlation doesn’t mean that it’s a sole reason (or even one of the reasons)
This could be because making transit free reduces the underutilization of large mass transit systems.
... the market will regulate everything. /s
For less dogmatic people, it may be useful to reflect on what else needs to be done to make public transit useful to more people, beyond the price.