I don't follow. Lobbying is paid for by corporations and organizations. The financial conflicts of interests that this poses on legislators is separate from campaign contributions. For instance, a legislator cannot use the latter for anything but campaign expenses [0]. But a legislator, after leaving office, can go to work for a friendly corporation (though there are laws requiring a "cooling off" period before they can directly lobby Congress).

[0] https://www.washingtonpost.com/politics/mike-pence-used-camp...