I don't think lobbying is a symptom of centralization. You see large concentrations around power centers because lobbyists will go wherever the people in power are. In a decentralized system, you'd still have lobbyists, they'ed just be spread out more.
Lobbying is a consequence of a professional political class. Those who make and implement laws need to be knowledgeable about laws, which is why such large numbers are lawyers. In a government that values competence and experience, those in high positions get there by spending years if not decades doing similar, lower level jobs. But if you spend your life in government, when would you have the opportunity to learn the intricacies of non-government life? What fraction of congress has actually worked on a farm? How many cabinet members have ever worked in a factory? How would a president know what it's like to be a refugee? Politicians need information from non-politicians to form and implement coherent policies that work for the people. Enter the lobbyist.
At its core, that's all lobbying is: relaying the views of interest groups to the people in power. We talk about it as a dirty thing because it is so easy for it to become a dirty thing, but it isn't inherently one. Unfortunately it's a slippery slope from legitimate lobbying to graft: even an honest politician will be more easily swayed by better presentation, more money allows a lobbyist to make a better presentation, lobbyists seek to align themselves with those who have money so they can make their better presentations, and soon enough the original cause is an afterthought.
That said, there is nothing about a centralized governance which makes lobbying easier, nor anything about decentralized governance that makes lobbying less necessary. Your local city councilman is just as clueless about the infinite number of things they didn't do instead of pursuing their path, and they are generally just as open to being wined and dined. Indeed local governments tend to be much more prone to graft than the central ones (though this may simply be due to the fact that there are so many more people to potentially corrupt).
Getting professionals in government the information they need to govern without giving undo influence to those handing them that information is a serious open problem in modern democracy, but decentralization doesn't seem like a solution.