I'd wager these are less cases of individual corruption than party-corruption aka horse-trading for influence and decisions. A classic problem parties have is

I'd wager these are less cases of individual corruption than party-corruption aka horse-trading for influence and decisions. A classic problem parties have is that they need to take care of their party militants and their families. This typically creates economic activities (insurance, banks, investment funds, charities, community organizations, ..) that are aligned on party lines. These companies are part of the party infrastructure and are used as power-bases to influence the party as well. It's called patronage and is rampant in western democracies.