I think Struber did a decent job. We had 9 points in 16 games when he took over and finished with 49 points, so we got 40 points in 30 games with him in charge. We lost the first 2 games, both unluckily, when he was at Oakwell, the second of these being 3-2 defeat at Blackburn, when we played some superb football. Tony Mowbray, Blackburn manager at the time, described our second half performance as being reminiscent of Real Madrid. After that game, i.e. in our last 28 games, we actually won more games than we lost. Additionally, we played some quite stylish football, if not always matching the standard of Real Madrid. Though we stayed up only because of the heroic performance on the final day of the season at Brentford, I fail to see how he could reasonably be described as the "luckiest manager we've had".
Up until the COVID break, we were playing some right *****. As bad as schopp and poya produced. He got lucky because of the break and when the league restarted, we were in a bit of a "win or bust" position so had to change style. I also think that playing in empty stadiums helped our young squad who had been getting pelters at home - I believe that is when Andersen was the Scape goat for losing the ball in his own area or kicking it out of play when they were instructed to tippy tappy about from goal kicks. Then there was wigans points deduction. I accept that after lockdown, we did play some quite nice stuff, but if we could do it then, why couldn't we do it before?
I'm sure you can ask the same question of every manager who had the team playing really well one season and crap the next. Or even half way through a season. See Darren Moore.