1.
conveniently; fortunately; by good timing
Things working out in a way that happens to suit the situation or the person. Can be genuinely positive.
2.
self-servingly; in a way that suits one's own interests
Interpreting or arranging things to serve one's own convenience or advantage. Carries a critical nuance, suggesting someone is being selectively convenient.
The adverbial form of 都合がいい (convenient, favorable). In sense 1, it describes fortunate timing or circumstances. In sense 2, it implies someone is being self-serving or naively optimistic. Context and tone determine which nuance is intended.