There is no single answer as to why the first five months of the season haven’t gone well for Barcelona.
If you think it’s because of Lionel Messi’s poor early start (by his own magisterial standards, as Ray Hudson would say), you are correct. If you think it’s because of manager Ronald Koeman’s insistence on the 4-2-3-1, you are also correct. And if you think it’s because of former president Josep Maria Bartomeu’s final destructive act, giving Luis Suarez away for free to a major rival and completely failing to replace him, you are also correct.
When 2021 began, Barca was languishing in sixth place.