As soon as '# of followers' became touted as a indication of political following, Twitter became bot infested.
The true number of bots was never disclosed.
There isn't an accurate public metric to judge the number of real users now or then, so the rest is guesswork.
As a public company, they had investment incentive to allow bots to the extent they could claim they're actual daily users. There may have been direct payments for that in addition to the blue check pay-offs. There may be other competing incentives that make eradicating them less the obvious choice it looks like now as a private company. (advertiser $ perhaps?) I don't think we know the actual user count, then or now. Lots of political grandstanding both times.