The author presents no evidence of these accounts being bots other than them being closely connected and cliquey. She makes that inference very quickly, and from then on, they are just referred to as "bots". I am 100% sure there are bots, but I am highly skeptical that Yang Gang is the worst offender here or stands out in any way compared to other campaigns. In fact a quick check on twitteraudit.com tells that he might be better than others, although I don't know how good their fake follower detection works.

I have been following this campaign since a few months, and I can attest that it has pulled in a large number of voters who were not politically inclined, the members are very passionate, and also that Yang Gang is quite cliquey and live in an echo chamber. Given those facts, I won't be surprised if those accounts were mostly real people.

Full disclosure: I like Yang.