From memory, his attempts to buy the club were stopped because Katharina used her veto due to the fact he could only carry out a leveraged buyout and was just fronting an investment group which would need to fundraise, rather than having a sole investor like Sport Republic / Dragan Solak.
He was pretty heavily criticised for the amount of debt he loaded onto Burnley in the process of that takeover and by all accounts, last season was shit-or-bust in terms of getting promotion. Got away with it, though.