Cube World is a voxel-based action RPG with a focus on exploration. It takes place in a procedurally generated fantasy world made up entirely of cubes. It is developed by Wolfram von Funck and his wife Sarah. An Alpha version was released in July of 2013. After some bugfixes the developers seemingly disappeared until Wollay began tweeting in 2015 about new features he is working on for Cube World.

Later Wollay disappeared from Twitter for 1,5 years between July 2nd 2017 and January 26th 2019. During this time frame he removed many key features from Cube World that the community enjoyed and added new completely different ones which redefined the core gameplay. Much of the quest variations were removed and he got rid of the old style world generation. Not much later he also removed the XP system. Many people in the community agree that the current version of Cube World feels more barebones than the Alpha did.
It's just not the same game but improved anymore that the community eagerly awaited for over 6 years... but something else. 
Just an inferior second version of the Alpha.

Developers will often keep older versions of their games saved. And content that may not have made it into the current version is also most likely saved.
There is no reason to assume he simply deleted them.
Here is one example of those features:
He first tweeted about capital cities on Oct 26th 2015 and last tweeted about them on May 28th 2017. There is a clear huge improvement we can see between the content showed off in those two tweets. He spent around 600 days at the least wanting to add something to the game, putting in a lot of effort and making huge improvements. .
He worked so much on it yet it's nowhere to be seen.
And that is only just one example of the many things he showed off but we never got. Another example would be the XP system. Which was scrapped less than half a year before release. Still visible in Jan 26th tweets but not on the July 3rd ones.

Wollay has already made an amazing game over 6 years ago that many of us spent hundreds of hours on. He spent 4 years afterwards turning it into a masterpiece...
We may never know why he brought something else to us after so long, but he still has to have the old files.
We just have to let him know it's what we always wished for and there was never a reason to rework it. And there could still be hope for this game.

Let's finally break the silence between the developers and the community. Afterall, to make a truly great game, you need both.
Cube World 2017!