The reason the Irish subsiduary was set up was that Irish laws were such that operating costs for an airline were much less than in the high-cost labour market of Belgium. It was anticipated that many of Virgin Express Belgium's routes would be taken by the Irish division, and some such as BRU-LGW and one daily BRU-LIN flight among others were operated by the Irish division.
However the collapse is due to the attempt at routes from Shannon. It competed against Ryanair and it seems clear that on most markets (especially smaller markets), two low-fare airlines competing does not work.
Virgin Express Belgium has also been losing money. Let's hope that too does not fall apart. Being sometimes based in Belgium, they are the only way to get free travel from Brussels to Europe.