ruin vs crumble

ruin is a noun but crumble is not a noun.

Word	Noun	Adjective	Verb	Adverb
ruin	Yes	No	Yes	No
crumble	No	No	Yes	No

As verbs, crumble is a hypernym of ruin; that is, crumble is a word with a broader meaning than ruin:

Other hypernyms of ruin include decay, dilapidate.

ruin (noun)	crumble (noun)
destruction achieved by causing something to be wrecked or ruined
a ruined building
an event that results in destruction
failure that results in a loss of position or reputation
the process of becoming dilapidated
an irrecoverable state of devastation and destruction

ruin (verb)	crumble (verb)
fall into ruin	break or fall apart into fragments
destroy completely; damage irreparably	fall into decay or ruin
reduce to ruins	fall apart
deprive of virginity
reduce to bankruptcy
destroy or cause to fail