I have read the following question and all the answers, and they do not answer my question, so it is not a duplicate:
Why are the vowels in Christ and Christmas different? (and other strange diphthong behaviour)
From wikitionary:
- Middle English Crist: /kriːst/, /krist/
- Old English: /krist/
The vowel in Old English was a short vowel /i/ but in Middle English, it became /i:/.
I read Homorganic Lengthening in this excellent answer by Janus Bahs Jacquet according to which vowels were lengthened before /mb nd ld rd ŋg/, but /st/ is voiceless.
Were vowels also lengthened before voiceless pairs? Why is this change in "christ"?