But then why did the FBI wait a few days before the election to announce a new batch of HRC's emails,
It's quite simple actually. Because they found that new batch on Anthony Weiner's laptop during a different pedo investigation and then they were going to cover it up, but decided it was too risky and by the time that information was relayed to James Comey they had no other choice but to release them!
"On Sept. 26, 2016, as part of a sex crimes investigation, an FBI agent in New York found hundreds of thousands of emails on a laptop belonging to former Rep. Anthony Weiner, who was married at the time to Huma Abedin, a top Clinton aide. Two days later, the head of the New York FBI office told dozens of FBI executives, including Deputy Director Andrew McCabe, that the laptop had 140,000 emails possibly relevant to the Clinton investigation. The next day, on Sept. 29, the New York office told several members of the FBI’s Clinton investigation team that the emails included BlackBerry messages. That was a red flag, because although the FBI had closed the Clinton investigation in July 2016, it had never found old messages from her BlackBerry account, which theoretically, was the most likely place to contain evidence of criminal intent.
The laptop was on a list of topics discussed by McCabe and other FBI officials on Oct. 3 and 4. And then … nothing happened. “After October 4, we found no evidence that anyone associated with the [Clinton] investigation, including the entire leadership team at FBI Headquarters, took any action on the Weiner laptop issue until the week of October 24,” says the report. Headquarters followed up only after being prompted on Oct. 21 by the New York office. Not until Oct. 27 did FBI officials brief FBI Director James Comey about the laptop.
By then, the bureau’s technical experts thought there was too little time before the election to go through the emails and determine whether any were incriminating. So Comey sent a letter to Congress disclosing what he could: that “the FBI has learned of the existence of emails that appear to be pertinent to the investigation.” Clinton sank in the polls. More than a week later, just two days before the election, the FBI announced that it had searched the emails enough to know that they wouldn’t change its decision not to recommend her prosecution. But the damage was done. She lost"
