Fallout 3 arguably made Bethesda one of the biggest developers in the gaming industry. The studio had earned a fanbase making quality games for years prior to reimagining this franchise, but while The Elder Scrolls IV: Oblivion in particular earned them new levels of recognition and success, it was the follow up of Fallout 3 that really catapulted them into the mainstream.
It was for good reason as well; despite being based on an older, niche series, Fallout 3 was one of the most influential and barrier-breaking games of its time. Its blend of open-world exploration and post-apocalyptic violence provided a perfect mix of experiences that could appeal to any type of gamer - and appeal it did.
Of course, essentially rebooting an inherited series so radically and successfully isn't exactly an easy or smooth process, and Bethesda experienced a whole bunch of roadblocks, complicated issues and happy accidents on their way to delivering their defining masterpiece.