Cynically, lobbyists are paid to find ways of bribing people without getting caught, or inventing forms of bribery that aren't illegal yet.
If by “cynically” you mean “inaccurately.” Lobbying involves making Power Points for staffers and doing their homework for them by drafting proposed legislation.
Lobbyists probably also tend to hire ex-politicians as a form of (perfectly legal) delayed bribery; and hire family members of politicians (https://youtu.be/jXf04bhcjbg?t=1493).