The finding is ‘not guilty’, rather than innocent. It does not mean the accused is innocent. It means they could not be proven guilty.

Important to note that in the original conception of western civilization, no one is 'innocent'. This idea that you have some secret special power to sniff out a persons true heart from a distance, which is separate from a jury of a persons peers studying and debating the evidence, is at best misguided and arrogant, and at worst a pernicious threat.