I agree with this definition (though it does omit the glaring problems with "providing a forum" which requires you to pay into). The problem is that this is not what you originally said:
> the intention of lobbying is to help politicians [...] make informed decisions by getting industry experts to advise them.
Lobbying is about getting different interest groups to put forward their point of view (that's what the definition you quoted effectively says), regardless of their level of expertise or credibility when it comes to the topic under discussion. This is completely antithetical to providing expertise to someone in power (which is what you were implying is the intention of lobbying).
You could argue that requiring expertise or credibility would result in a technocracy, and that allowing ordinary people (who don't necessarily have education or expertise in a topic) to lobby is more equal. And in theory it would be more equal. But lobbying costs time and money, which are things that ordinary people don't have in abundance. So the system is already favouring groups of people that have bigger bags of money -- so surely favouring people that have bigger stacks of research would be a better solution overall.
The practice of lobbying provides a forum for the resolution of conflicts among often diverse and competing points of view; provides information, analysis, and opinion to legislators and government leaders to allow for informed and balanced decision making; and creates a system of checks and balances that allows for competition among interest groups, keeping any one group from attaining a permanent position of power. Lobbyists can help the legislative process work more effectively by providing lawmakers with reliable data and accurate assessments of a bill's effect.
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An excerpt from the legal definition of lobbying. My own take is a bit lacking on the "resolution of conflicts" portion, but still in line with the intended outcome - informing politicians on matters they wouldn't otherwise understand. That said, its definitely not as pristine an occupation as we would hope, with all the people involved in it.
Another take on the topic:
https://en.wikipedia.org/wiki/Lobbying_in_the_United_States#...
It's worth noting that lobbiests can and do also work at levels incapable of affording expert panels or independent investigations, such as the city and state levels.