Most Successful Pivot

[TallSilhouette]

I was watching the trailer for an update to Ready Or Not today and thinking about how it started out in testing as a competitive 3v3 shooter iirc before wisely pivoting into a more SWATesque PvE shooter. 

What are some other successful pivots in gaming where a lackluster product was saved by a radical shift in design or focus? The later in development the better. 

Spoiler!

Fortnite is probably the most successful example but I'd love to hear others. 

Cheers.