这整个"好主意最后被搅和成了错误决策"的process就是groupthink。你直接结尾加一句this is how groupthink leads to their decision不就够了么
如果非要在里面提一下哪儿是groupthink的话,如果是我就会说"original supporters changed their minds so as not to confront with the manager--that's when groupthink comes in--because they dont want to leave a bad impression on him."