The history of the alphabet is quite complicated and various cultures repurposed letters as it suited them.
Did you know that F, V, U, W, and Y all originated as forms of a single Greek letter that the Greeks themselves discarded early on.
The Greeks inherited an alphabet with no letters assigned to vowel phonemes, so they repurposed several of them.
When the Latins learned the alphabet from the Etruscans, they used C (developed from Greek Γ) for both /k/ and /g/ phonemes, casting K aside for the most part. They kept QU for the /kw/ combination, but otherwise, ignored Q.
Eventually, the Romans decided they needed to distinguish /k/ and /g/ in writing and split C into C and G.
The process of palatalization morphed the pronunciation of C in languages that leaned the alphabet from the Romans, so now it might not only stand for /k/, but also /ç/, /ʃ/, /ts/, /tɕ/, /tʃ/, and /s/.
English originally didn’t use K, using C only for /k/
This was the original English alphabet
A Æ B C D Ð E F Ᵹ/G H I L M N O P R S T Þ U Ƿ X Y
F had two allophones: /f/ and /v/
S had two allophones: /s/ and /z/
Ƿ was for /w/—W hadn’t been invented yet
Ð and Þ were for /ð/ and /θ/ as in “this thing.”
Æ was for a low front in rounded vowel that we now mostly treat as /æ/
H and G had several allophones each.