I'd argue that political stability consists of and depends on at least rule of law, separation of powers and democratic representation. The EU and its member still have a lot to progress in this regard, though. Coalition building is kind of a comprise towards building pluralistic quasi-consensus based decision-making.

IMO, coalition political systems have the potential to politically deal better with long-term issues as small parties can influence governments beyond a single term. Green parties, but unfortunately also far-right parties, for example can thus push for their topics.

The US also had a coalition, the National Unity Party during its Civil War.