If Twitter clamped down on bots on the site/network it could end up revealing a very unflattering (to investors) picture of the sites true user traction.
The site has struggled to grow to its targets and has a significant issue with people creating accounts and quickly abandoning the site.
So Twitter has a very large incentive to do nothing about the bots.
1. Bots degrade the experience for the regular user. The site feels less authentic with bots, and the quality of the content overall goes down. If you're trying to get eyes on Twitter, bot content does not help you.
2. Bots are not helpful when looking at your ad metrics. Bots are not actually viewing ads and are not interacting with them. If you're goal is to get actual eyeballs on ads, and showing those ads have impact then bots make your site look weaker.
So, if I like what he is really doing, sure, I might follow him back. Otherwise, no way.