The 'most succesful manager in 50 years' argument is too simplistic.
The PL's commercial success has brought about an influx of top foreign coaches and players which has had a massive positive influence on English football.
The PL academies are churning out large numbers of technically gifted players who are the equal of any other country.
Globally it seems that the gap between the traditional giants (Germany, Italy, Brazil etc.) and the minnows is greatly reduced.
All these factors have almost guaranteed that England will go deep into major tournaments.
This is the situation that GS found himself in and in crude statistical terms it gave him a huge advantage over previous England managers like Robson, Taylor etc.
I don't hate GS, I pity him. He was clearly out of his depth and while I wish him well, I'm glad he's gone.
In my lifetime WC qualification groups have gone from 3 teams playing a total of 4 games & less countries to more teams & seedings fixed & play offs ensuring it’s almost impossible not to qualify.
In 74 Poland edged us with Wales 3rd
In 78 Italy edged on goal dif cos they scored more vs Luxembourg
In 82 we qualified & won every group game v France, Romania & Kuwait & rewarded in the next round, group of 3 including Germany & Spain. We drew both & were out with 3 wins & 2 draws.
In 86 we lost to Maradonas Argentina & 90 on pens in the semi to champions Germany.
In 94 we missed out to fantastic Dutch team worth noting that Ajax were European champions in 95.
In 98 Argentina after Beckham red carded.
In 2002, R9, Ronaldinho & Rivaldo put us out.
Any need to go on…….
So for context the European ban affected us & English players were disadvantaged.
The premier league is now the richest league in the world & we have investment in an academy & now win tournaments at all ages.
Qualifying is an absolute certainty now & just in case we struggle we’d get the benefit of play offs.
He got lucky with draws & has massively underperformed with the resources at his disposal & the myth he was successful for going further is flawed when the context is considered.