was the goulification on purpose or a bomb fall into it ?

I got a little ways into it but my character wasnt strong enough i died fending off all the ghouls .-. maybe later when i have more rad away and health ...

was the crazy lab test to see how humans reacted to radiation ?

Read. The. Wiki.

During the Great War, Kool-Aid man burst through one of the walls screaming "OOOH YEEEEAAAH!!!"
The hole he left in the wall allowed for radiation to leak inside, thus all the residents are ghouls.

Once you play Old World Blues, you'll find that the Kool-Aid man was created when a pitcher and a lobotomite were spliced. Also, there are rumors that if you kill Caesar's Legate at the end of the game, Kool-Aid Man will replace him as legate in Fallout 4.

The Vaults reactor was damaged during riots. People wanted out and they damaged the reactor.

Note that that happened long after the Boomers left Vault 34.

Edit: So this is a case where the wiki is wrong or at best misleading.