BBM....I think the digital forensics examination on KAK's devices was done by the ISP, not the FBI...JMO.
If I go back to the probable cause affidavit, where Detective Vido lays out the CSAM case against KAK, it says that while working a certain ISP case (redacted - my guess is, it's the murders of Abby and Libby), the FBI forwarded to the ISP the information that an adult male was soliciting underage females using the Anthony Shots profile. Based on the information, subpoenas were sent to SnapChat and Instagram that determined the IP address that was being used, and it was traced to the Canal St House in Peru, where the ISP and the FBI jointly executed a search warrant on 2/25/17.
However, we also see in this affidavit that the digital forensic examination of the devices seized in the Canal St search was eventually given to Detective Vido in June of 2020 by Indiana State Police Sgt. Chris Cecil. If you Google him, he's the assistant head of the ISP Cyber Crimes Unit...one of ISP's top experts in internet crimes against children. So I don't think the FBI was responsible for not sharing relevant information from the devices. I think that examination was primarily done in-house by the ISP, by their Cyber Crimes unit team based in Indianapolis. I have no idea why it took so long, but there were a lot of devices and apparently a lot of material. As
@TL4S said, it's not like KAK stumbled across a few images here or there. He had how many devices filled with this material or digital traces of it?
It seems crazy to me that it would take over three years, but the digital examinations are also more complex than what the public knows. I can't make any conclusion yet about whether the length of time of the investigation is due to someone dropping the ball on the extraction of the data or if that's just how long it takes. I don't think it was so much that information was not shared between agencies, as information was not yet known.
Here's a link to the probable cause affidavit published by local news WISHTV:
https://www.wishtv.com/wp-content/uploads/2021/12/Kegan-Anthony-Kline-PC.pdf