Complex sentence: Most importantly, he had made it possible for water to be piped to every room, a laundry was added and most significantly private bathrooms contribute to a resurgence of the hotel's popularity, because few hotels offered such extravagances.
Split into simpler sentences: Most importantly, he made it possible for water to be piped to every room. A laundry was added and, most significantly, private bathrooms contributed to a resurgence of the hotel's popularity, because few hotels offered such extravagances.