physical constants - Why is the speed of light exactly $299,792.458$ m/s and not faster or slower?

Why is the speed of light $299,792,458$ metres per second, and not faster or slower.

Why not $500$ trillion kilometers per second or $120$ miles per hour?

This has been 'bothering' me for a while. Googling it usually found answers about why isn't '$c$' infinite et cetera, and the answers were usually saying (from my interpretation) that if $c$ were infinite, then matter couldn't exist.

I recently found this reference, but despite its blatantly obvious attempt to explain to laymen, I still don't understand why $c$ is (roughly) $300$ million meters per second.

A 'dummy's' guide to my understanding why '$c$' is the number/speed that it is, would be greatly appreciated by me and all others who will read your answer in the future.