While Leicester's financial issues are one thing it's not unheard of sides to drop not long after relegation from the premier league....we did it ourselves!
Last 10 years:
2015-16: Newcastle United (promoted), Norwich City (promoted 3rd season*), Aston Villa (promoted 3rd season*)
2016-17: Sunderland (relegated), Middlesbrough (still in Championship), Hull City (relegated 4th season)
2017-18: Swansea City (still in Championship), Stoke City (still in Championship), West Bromwich Albion (promoted 2nd season*)
2018-19: Cardiff City (relegated 6th season), Fulham (promoted*), Huddersfield Town (relegated 5th season)
2019-20: Bournemouth (promoted 3rd seasons), Watford (promoted*), Norwich City (promoted*)
2020-21: Fulham (promoted*), West Bromwich Albion (still in Championship), Sheffield United (promoted 2nd season*)
2021-22: Burnley (promoted*), Watford (still in Championship), Norwich City (still in Championship)
2022-23: Leicester City (promoted*), Leeds United (promoted 2nd season*), Southampton (promoted*)
2023-24: Luton Town (relegated), Burnley (promoted*), Sheffield United (still in Championship)
2024-25: Southampton, Leicester City, Ipswich Town
It's getting more common for teams to either go straight back up or straight down. No side has been promoted after an absence of more than 3 seasons - ie once the parachute payments run out - although Boro may buck that trend this season - but a there's an increasing trend of clubs circling the drain once the PPs run out.
Still in the Championship: Middlesbrough (9th season), Swansea (8th), Stoke (8th), WBA (5th), Watford (4th), Norwich (4th), United (2nd)
Promoted: Aston Villa (3rd season), Norwich (3rd), Bournemouth (3rd), WBA (2nd), United (2nd), Leeds (2nd) Newcastle (1st), Fulham (1st x2), Watford (1st), Burnley (1st x2), Southampton (1st), Leicester (1st), Norwich (1st)
Relegated: Cardiff (6th season), Huddersfield (5th), Hull (4th), Sunderland (1st), Luton (1st)