I expect any European football is the league expectation for Frank with decent player investment.
Did the club not give Postecoglou significant resources to do his job? He won the Europa League after all.
There won’t be decent player investment
The club gave Postecoglou a slashed wage bill 2 seasons in a row and 3 teenagers in season 2 with the expectation to integrate academy kids. He himself said he was building a team for 5 years and the club seemed to be on board with it.
When everyone saw that using teenagers for depth in the PL gets you in trouble, Levy and Lange threw him under the bus and acted like they were never part of this idea to build a team for 5 years.
Winning a trophy happened despite the club, not because of it.