In retrospect of this terrible year.. has any team ever fallen quite so fast?
In 2016, only THREE years ago, Valtteri never failed to get out of Q1 and reached Q3 14 times, after doing so 18 times in 2015 with an average qualifying position of 6th!
by 2019 they are the worst car on the grid often by seconds a lap.
Is it just a catastrophic job by technical leadership, now fired and replaced? Or is is just money and they are doomed?
This has happened to all sorts of teams, including Ferrari, twice. See their 1962 or their 1980 seasons. Lotus also didn't take long from being race winners in 1987 to struggling to qualify in 1989.
The team obviously has had major problems in its engineering department that seem to stem from Paddy Lowe's appointment after Pat Symonds left. The resources are there as you say, from 2014-2016 (even 2017 wasn't too bad). Something hasn't been working lately and maybe with a new engineering leadership structure in place they can get back up there. In modern F1 it's very hard to transform a car over a season.