As a verb crumbled
is (crumble).
As a noun crumbler is
agent noun of crumble; one who crumbles.
crumbled
English
Verb
(head)
(crumble)
crumble
English
Verb
(en-verb)
To fall apart; to disintegrate.
To render into crumbs.
Noun
A dessert of British origin containing stewed fruit topped with a crumbly mixture of fat, flour, and sugar.