The essence of the case was that the EU alleged that Ireland's Government and tax authorities made individual tax arrangements to facilitate individual corporate bodies, notably Apple. Ireland' case was that no specific aids were provided and that all rulings were generally available to all companies, operating 'a level playing field' in its tax policy.
See also the Department of Finance statement: here.
In ruling against the EU Commission's contrary interpretation, Ireland's case was justified, and could be regarded as a result involving some embarrassment for the Commission.
It comes just days after Ireland's Finance Minister, Paschal Donohoe was elected chair of the Eurogroup, the Eurozone's policy committee of finance ministers, a considerable honour for a Finance Minister from a relatively small member state. It is also a vindication of a controversial position Ireland has adopted in relation to its tax policy, at a very important time for the economy, as the financing of the Covid-19 pandemic reaches a critical point.
In a statement, IDA Ireland welcomed the decision. It said: "Ireland has one of the most consistent, competitive and transparent taxation regimes in the world and together with our other offerings of excellent talent, access to the European market and stable pro-enterprise policies, Ireland has been hugely successful in attracting foreign companies to establish and expand in Ireland".
For Background see this article from the Finance Dublin Article search archive.