Think about how we got here
Very early on we out sourced a big chunk of the election process to volunteers, fans, fanatics if you will. Why raise taxes to pay for elections?
Parties took over the preliminary parts of the process in exchange for vetting potential candidates.

OK so I’m guessing but, no one works for free
The Pay may not be cash, power, influence, patronage are all nice.

Money has always been speech
Excess resources have always been required to have a meaningful political opinion

The system was designed for information moving at the speed of horse at great expense
The system was to serve 1% of the present population

Damm thing works better than one would expect :D