Bonjour Debra,

Alan and Chris are both correct that it is Le Conditionnel Passé - deuxième forme - which is rarely used - and it can be replaced by Le Conditionnel passé : Qui l'aurait cru ?

Take a look here: https://lecritdentreprise.com/qui-leut-cru-ou-qui-leut-cru/

I hope this is helpful.

Bonne journée !