>>509021631just change the definition of happy
first, monopolize education (or create a lack thereof) to shape the idea of what happiness is supposed to be
and then control any and all access to information in order to properly depict the ideal of happiness
and then destroy every evidence of life before that, so no one had any ideas of what happiness is supposed to be
then you can create an environment where the best you can hope to achieve is what would otherwise be qualified as unhappiness
and FINALLY, you will have: the jewish christian dark ages