I can't say how I know due to attorney-client privilege, but I know that Joe Biden took money from Burisma personally. They'll never actually find the real transfers for a lot of reasons. The "10% for the big guy" might be the closest we get in open source documents.
As for Shokin, the EU wasn't investigating him. It was only after Polish ex-president Alexander Kwasniewski pushed them that they and the IMF "agreed" with Ukraine liaison Joe Biden. Kwasniewski was on the board of Burisma, too. Funny, that.
Oh, and let's not forget what the Ukrainian parliament did - they couldn't find a reputable attorney willing to act as chief prosecutor and not investigate Burisma, so they CHANGED THE UKRAINIAN LAW ON THE CHIEF PROSECUTOR TO REMOVE THE REQUIREMENT THAT HE HAVE ANY LEGAL BACKGROUND WHATSOEVER, in an emergency session, to find a hack willing to play along with Biden's demand.
There aren't any conspiracy theories there. It's all pretty open and brazen. Kwasniewski lobbied the EU and IMF, Biden lobbied the US, suddenly everyone speaks "in unison" and then suddenly Ukraine has to replace him with a political hack with no legal experience or law degree.
ἡ δὲ κἀκ τριῶν τρυπημάτων ἐργαζομένη ἐνεκάλει τῇ φύσει, δυσφορουμένη, ὅτι δὴ μὴ καὶ τοὺς τιτθοὺς αὐτῇ εὐρύτερον ἢ νῦν εἰσι τρυπώη, ὅπως καὶ ἄλλην ἐνταῦθα μίξιν ἐπιτεχνᾶσθαι δυνατὴ εἴη. – Procopius
Ummaka qinnassa nīk!
*MySmiley*