How do teams go from perennial Champions League participants to being rooted at the bottom of the league? They finished 2nd just two seasons ago.
First of all Schalke haven't really been perennial CL participants for a while and their 2nd place three seasons ago was a perfect storm of competitors having an off year (e.g. Leipzig having the 2nd season hangover and Dortmund having their abyssmal Bosz/Stöger year, Gladbach finishing midtable), not having to deal with EL/CL and grinding out a ton of fortunate narrow wins. They were already sliding into the abyss back then.
A look at the personell from that time also says a lot:
Fährmann - Captain, axed for Nübel, who thanked them with a litany of blunders and a
free move to Bayern
Naldo - the boss of their defense and actually 2nd best goal scorer, got axed and sold
for peanuts during the following season, because he got too old for Tedesco's liking
Kehrer - sold to PSG
Caligiuri - a leader, someone who steps up with crucial goals - let go on a
free to Augsburg this summer, replaced with a loanee from Salzburg who is out of his depth in a top league
Meyer - was their midfield orchestrator, lost on a
free to Palace, replaced by Rudy for €20m, who reportedly took a huge pay cut, so he wouldn't have to play for Schalke this season
Goretzka - no words needed here, lost on a
free to Bayern
McKennie - loaned to Juve
for peanuts
Harit - by far the most talented footballer at the club, currently suspended, hasn't scored a Bundesliga goal in over a year now I believe
Burgstaller - their top scorer that year, 2nd division player who had two good season, before he reverted to his usual level and is currently loaned out to St. Pauli
They basically lost or axed their entire upper squad hierarchy, they sold/lost most of their good players and their replacements flopped. Now their squad has some gaping holes (especially on the wings) and they are leaderless, there is basically no one who takes charge on the pitch. Which also mirrors their management structure, where people are dropping like flies: Tönnies finally had to resign last summer, their CFO went with him, out of the three people who more or less make up the DoF role at their club one left in the summer, one (Reschke) got sacked last week after little over a year on the job and their boss, Schneider - on the job for about 18 months now, will reportedly soon follow.
It really is incredible how fecked and hopeless they are for a club that probably still posts the third highest revenue numbers in the country. At the moment it seems like their only saving grace could be that the bottom of the league has been very weak this year (though some teams like Mainz and Cologne have gotten results lately).