Final answer:
During the Romantic era, after Wagner's influence, Giacomo Puccini rose to prominence with popular operas such as 'La Bohème' and 'Tosca.' Popularity can vary based on timeframes and cultural shifts in musical taste.
Step-by-step explanation:
When looking for an opera composer who gained popularity after another composer's retirement, it's essential to consider the historical context of different musical eras.
For instance, Richard Wagner, a composer known for his innovative operas, greatly influenced the genre. Following his era, composers like Giacomo Puccini began to rise in popularity, especially after Wagner's passing. Puccini's operas, such as 'La Bohème,' 'Tosca,' and 'Madama Butterfly,' are viewed as staples of the operatic repertoire even today.
Of course, it's worth noting that popularity can fluctuate and new talents constantly emerge, so identifying a single composer who took over from another can vary based on the specific timeframe and cultural shifts in musical taste.