What does “crawl over a pile of hot coals” mean?

Solution 1:

It is not a set phrase. In your example, the sentence is being used as hyperbole (or exaggeration). The writer is trying to convey that Kelley would have done anything in order to make the interview, even something as extreme as crawling over coals.

Although your example does not use a set phrase, there are several other coal-themed idioms in English. These include

• to rake someone over the coals (to scold or reprimand someone)
• to rake over the coals (to dredge up past issues)
• to walk on hot coals (to be in a situation that could easily turn worse)

Despite their apparent similarity to the example you cite, variations on these idioms are not intended by the writer of your passage.

Solution 2:

'Would crawl over a heap of hot coals' isn't a set phrase, but it is a variation of Would walk over hot coals, which is. Would walk over hot coals for/would sooner walk over hot coals than... conveys great dedication to the person or circumstance that you would walk over coals for/in preference to, such that you would be prepared to risk your own personal safety for their benefit or to avoid that circumstance. Usage examples

Colin would walk over hot coals for his best friend

She'd sooner walk over hot coals than ever swallow her pride

Assuming that the use in relation to a person, rather than a thing you don't want to do is the more common meaning as the balance of google results suggests, it might possibly be linked to the bible verse Proverbs 6:28-9 which likens the certainty of punishment for adultery to the certainty of burning when walking on hot coals.

Or can a man walk on hot coals And his feet not be scorched? So is the one who goes in to his neighbor's wife; Whoever touches her will not go unpunished.

Given that we all know it is possible to walk on hot coals without getting burnt if you are quick enough about it, I am not sure what this means for the biblical pronouncement.

EDIT: the phrase 'crawl over a heap of hot coals' may also draw on the phrase 'crawl over broken glass' which has similar meaning to 'walk over hot coals' but in my observation, tends to be used more to express something you would endure to satisfy your own desire for something, rather than having any altruistic connotation.