If, and I do believe this, that Zelensky wants Ukraine to remain sovereign and not a Russian vassal state, He'd likely dance with the Devil to keep the Russians out.
If he's dealing with Biden, there is corruption built in. It does not mean Zelensky is getting rich off of this (he was already rich when the Russians invaded), but Biden and those in his network from the days of his Vice Presidency likely are siphoning off a lot.
Which is why so many of us wanted materiel support, and not very much cash.
Between the Holodomor, the mining waste and complexes contaminated like Zhovti Vody, and still not dealt with (likely some Oligarch, somewhere, is keeping it that way), the Ukrainians have plenty of reasons for not wanting Soviet Russian control of the region.