Greater Netherlands

[The Lawspeaker]

No, you have to nuance this a bit.
The Flemish were more catholics than the Walloons. Walloons disliked the Orange rule a bit and the Flemish didn't like it for religious reasons (protestants vs catholics).
First the difference between Flemish and Walloons weren't so clear-cut than today, as both regions didn't even exist.
Second, the modern dutch-oriented Flemish identity was formed during the 20th century through the standardized Dutch language taught at universities (Ghent and Leuven), but back then the Flemish and the Dutch were very different. The Dutch considered the Flemish backward peasants. It is Neo-flemish romanticism that makes some Flemish think "oh, had the Netherlands not split, it would have been better", but their ancestors had another idea. They don't realize that the context was vastly different.

Now, Flanders and NL became "closer" due to modern Flemish identity being vastly influenced by the Netherlands, religions are mostly irrelevant today, and the shared Euro currency, the cultural exchanges, medias and education and a similar quality of life, made both countries much closer to each other than back in the 19th century.
Meanwhile, it is only quite recently that the cultural exchanges between Wallonia and Flanders went to an halt.

While it should be the case that all parts are influencing each other.

[Albion]

but back then the Flemish and the Dutch were very different. The Dutch considered the Flemish backward peasants. It is Neo-flemish romanticism that makes some Flemish think "oh, had the Netherlands not split, it would have been better", but their ancestors had another idea. They don't realize that the context was vastly different.

So a bit like how London and the South East think about the North and South West then.