They are still subpoenaing bank records. Once they have them all they will track the money. Then they will look at timelines and see what policy decisions were made around those money transfers They will track phone calls on cellphones, look at those timelines, see who was talking to who. They will even subpoena speech writers to see if there were last minute changes made about Ukraine corruption. If those changes about the prosecutor were made immediately after the Burisma guy or Hunter called Joe, the Bidens will be in serious trouble.
Investigators are smart. They will find evidence if Joe is guilty, which he almost certainly is.