riuscivano
Riuscivano is the imperfect indicative form of the Italian verb riuscire, third-person plural. The verb riuscire means to succeed or to manage to do something, often conveying a sense of overcoming a challenge or achieving a result.
In Italian, riuscire is commonly used with the preposition a followed by an infinitive to express being
The form rius(c)ivano follows the regular imperfect endings for -ire verbs: io riuscivo, tu riuscivi, lui/lei
Riuscivano can be contrasted with non riuscivano, meaning they were not able to; the negative expresses failure
See also: riuscire, imperfect tense in Italian, verb conjugation patterns for -ire verbs with -isc- behavior