Because it isn't like the movies. You first have to gather the evidence before you decide to charge. They were sorting through the paper trail to dot the i's and cross the t's.

Your question just sounds like it wants a conspiracy theory. Law doesn't move quickly even in normal circumstances. Just look at the EAR/ONS case, where he was charged in April 2018 and sentenced over two years later, that's after a thirty+ year investigation, with renewed interest 2 years prior to the charges.

Secondly, I'm sure anyone who has ever held a job understands that you often have more than one task to complete at a time and that sometimes, those tasks can't move forward until someone else does their part. Throwing all of the money and resources in the world isn't always going to make something go faster, sometimes it's just a waste of those resources.