> Many if not most career politicians have education in their domain

They don't have "domains", they are career politicians. It is nice when a politician has some experience in the topic they're legislating on but the system works by having generalists who bow in whatever direction winds are blowing the most money from.

It is not possible to be an effective career politician by having firm principles or technical expertise. It requires a near total dedication to politicking. If they happen to have knowledge of a topic it is coincidence because the number of political topics is large and the number of politicians is comparatively small.