Piling on charges often means doubt about the prosecutable odds on the case, so you get them on something.
Although, with all the known evidence and all the additional evidence that we don’t know about, I don’t know why there would be doubt about this.
The feds get a 98 percent conviction rate with their pile ons.
Nigel Farage once pointed out that the federal piling on of charges here in the USA meant you could only mount a credible defense with expensive lawyers.
Either that or cut a plea deal where they get you on something as you noted.