what does this idiom mean in this song....

[guliver]

"Fell right through the cracks"

Jason Mraz - I'm Yours Lyrics [Original Ukulele Version] - YouTube

I think fall through the cracks means be overlooked, ignored... but doesn't make sense in this context from videoclipe

Please, help me!

[catbert]

"Fall through the cracks" does normally mean to be overlooked, but I think this songwriter is using this expression to mean that he collapsed into pieces and literally fell through the cracks. In the preceding line he sings "you were so hot, I melted".

[guliver]

It's the same "fall through" = to fail in this context, am I right?

[5jj]

It's the same "fall through" = to fail in this context, am I right?

It's difficult to tell with song lyrics, which are sometimes close to meaningless. In this case, I think catbert has come as close to any meaning as one can.

[catbert]

It's the same "fall through" = to fail in this context, am I right?

No, it doesn't mean "fail" in this context.
The songwriter just used this phrase because he thought it would sound nice, not because it's actually meaningful in the given context.