I notice for all the tweets shown from Nov2017-Jun2019, the Eco SE twitter account doesn't tweet bounties and there are no tweets for the past year.
Why doesn't the Eco SE twitter account tweet bounties?
Why no tweets for the past year?
Some information about how the Stack Exchange Twitter bots work can be found here on Meta Stack Exchange: How does the twitter bot work?
However, this is not the official bot for Economics Stack Exchange. An earlier version of this site had one, https://twitter.com/StackEcon, but this account is now deleted. According to Who runs the Econ SE Twitter account and how can we reactivate it?, the account you linked to is/was maintained by one of the moderators. That explains why it tweeted YouTube links, and also why it hasn't tweeted in a year.
FYI: bountied questions can be tweeted by the official bot if they're hot enough, but there's no guarantee that they will.