Yes, the hype around Jovic was funny. And the thing is, he didn't even produce fantastic numbers in Bundesliga that would somehow justify the transfer sum. We are talking about a player who had one good season where he scored in the double figures, 17 goals - good season, sure, but not exactly setting the world ablaze for a striker.
That's why I'd argue that what propelled that whole Frankfurt attack into the spotlight of hype and transfer desire (it's not just Jovic after all - Haller too had a big money move that flopped, after scoring 15 goals ONCE in Bundesliga in his mid 20s; Rebic was touted to go to all kinds of big clubs and is now doing okayish at Milan..) was not so much their league campaign but their awesome, surprising, spectacular David v Goliath Europa League campaign where they made it to the semis against all odds, topping a group with Lazio and Marseille and beating Shakhtar, Inter, Benfica to make it close vs Chelsea. Jovic scored 10 goals in that campaign.
Without that run, I wonder if anyone would be so giddy as to pay 50m-60m € for strikers with such an ultimately unimpressive record in Bundesliga and somehow expect them to be prolific world beaters.