It’s rare for a politician to only work 4yrs at the policy making level. Most of them are career politicians these days or retired wealthy people, not people with regular jobs giving politics a shot. Yet they all seem to be wealthy in the US, even after years of public service, regardless of their overt stance on business politically. Which is something the big firms can always rely on.
Now if you’re a politician in a democracy, you know it may be all over in about 8 years, so it’s more your interest to cosy up to the companies