While signing both Caicedo and Enzo are obviously clear mistakes since Chelsea willing to spend money double from their market value just because they have a lot money.
I wouldn't say Chelsea made a mistake signing Enzo Fernandez and Moises Caicedo, they are both excellent midfielders that any manager would wish to have in their side, and they are also very young, Enzo is 22 years old, whilst Caicedo is 21, thus they are for the present and the future (if they decide to stay in Chelsea for the long term).
What i don't agree with is the signing fee for these players, it is definitely ridiculous and far above what their valuation should be, but i guess it is what it is, the transfer market these days is a joke, so much money being thrown around on players that don't even merit it.