I think his comment his written to imply that it is possible for this to happen. In which case, it does not require supporting evidence beyond the logical consistency of itself, which is sound, I believe.
They are real people, aren't they?
to who?
The entrenched who already have a mass information platform available to them (news).
I shouldn't have to google for someone as politically active... ...you're literally working to elect someone president.
Both Hirschfeld and Osborne first logged in to their accounts in February 2011, well before the first known IRA activity in 2013. WIRED’s analysis found at least 63 accounts created between 2009 and 2013 included in the list provided to Congress.
It's reasonably well known to anyone who's used the site that old accounts are fairly frequently hijacked by others, so this doesn't invalidate Twitter's claim.
[0] https://media.ccc.de/v/34c3-9268-social_bots_fake_news_und_f...