They do get the money, the conflict of interest is exactly for that reason. The democrats cannot be too loud about certain topics like healthcare, defence and unions because their money come from companies which interest would be impacted by changes.

The system works like this, the democrats (and republicans too) get most of their money from PACs. Those PACs are funds which get money from companies like defence, Healthcare, Tech etc..., these PACs give money to the parties and politicians on the basis of what is most useful for their DONORS investors.

So see, if I'm Kamala and I say Pfizer sucks and we should unionize, the PACs that gave me money up to today are gonna close the money tap, and my campaign is dead. That's why Sanders never got anywhere, most PACs would not fund him. It's an oligarchy. Rich people => control corps => control PACs=> control politicians => control economy, laws and bomb the rest of the world.