I'll agree that Levy's support is a problem, but the managers were a problem too.
The 18 months between Moura in Jan of 2018 and 2019's summer signings of Clarke/Ndombele/Lo Celso significantly set the club back. Poch was coming off a miraculous run to the UCL finals, dealing with aging players, malcontent players, and injuries when he got sacked. Not getting any players in those 18 months doomed Poch and the club. Then, Levy got wide-eyed at Mourinho being available and brought him in thinking it was a quick fix and that he could win with the current squad. Not having to spend anymore money appealed to Levy, and set in motion the events that led to some miserable futbol over the last 4 years. Jose, interim Ryan Mason, NES, Conte, interim Ryan Mason again. No real consistency, and we got away from our style of play.
A churn of squad philosophy impeded any meaningful transfer business. You only have to look at Bissouma's performance under Conte and his performance under Ange to see that. Conte didn't know how to use Bissouma (who was also injured). We had squads that weren't congruent with their managers' style of play. Now, Bissouma is playing for a manager that gets him, and our midfield looks legit.
Conte checked out less than a year after getting hired, Jose lost the team, and NES was never going to work out. All of that is on Levy, in addition to his unwillingness to spend.