Why is the speed of light 299 792 458 metres per second and not any 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 etc. and the answers were usually saying (from my interpretation) that if c were infinite then matter couldn't exist.

I recently (a month ago) found this (https://aeon.co/essays/why-is-the-speed-of-light-the-speed-of-light) but despite its blatantly obvious attempt to explain to laymen (and re-reading it several times), I still don't understand why c is (roughly) 300 million metes 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 that will read your answer in the future.