We also have the well known kinetic energy formula

E = 1/2mv^2

So, this also means that mass can be converted into energy??????

I don't think so.

So why does E = mc^2 say that?

It only differs in that v=c and a factor of 1/2.

Betcha you can't answer.

Try this for an answer:

https://franklinhu.com/emc.html

E=mc^2 = 1/2mc^2 + 1/2mc^2 which is the expected release of kinetic energy from an inelastic collision of two objects at the speed of light.