Belgian requirements have a strong tendency to morph into a form that matches the offer with the largest bag of carrots attached*. France just flew in with a Rafale carrying 20B carrots. Thats a lot of persuasion.
Secondary is that no one in Belgium really knows what its military role is since the fall of the wall. The mission flip-flops as defense ministers come and go. One government opted for a disaster relief mission that gave the military a fully engaged role, had broad popular support and scored quite a few brownie points abroad. However, it mostly involved the C130 fleet and its crews. Then came Crembo, who thought that was unmanly, ditched it, and instead sent our F16s to kill little brown men with AK47s. Queue lots of internal discontent and the evaporation of the brownie points. Belgian F16s had homebrew avionics and AFAIK never quite got the real deal, so they only operate on the periphery.
* Carrots may be for public consumption (as with the F16 purchase), or private enjoyment (Agusta A109 purchase, 1985 artillery shell purchase, ...)