Why do you use "to ever happen" and not "that ever happened"?

Is there a rule for this I can learn? We read a text yesterday, and the sentence contained the phrase "the biggest disaster to ever happen". The full sentence was:

"The sinking of the Titanic was one of the biggest maritime disasters to ever happen.."

Why do we not say "The biggest disaster that ever happened" if it was in the past? Is there a difference between the two?

Thank you.

Solution 1:

Both versions seem alright to me. In the English Corpus (many English books over the years) the phrase that ever happened seems to be used much more than to ever happen.

Consider this ngram comparing the two.

This ngram considers "(*) that ever happened" in which (*) is replaced by other words (the ones which occur the most). It shows thing that ever happened and things that ever happened are more common than to ever happen.