In retrospect this would have made most sense. Amrabat first choice, Lavia gradually taking over, as I assume was the plan with Fabinho before the Saudis came in for him.
My guess is they were waiting for Tchouameni in case Real needed to raise money for Mbappe.
When it became clear that Tchouameni was no go, and with Southamptom refusing to budge on their valuation for Lavia, the club - flush with unexpected income from Fabinho and Henderson - pivoted to Caicedo.