Emerick On John's Personality Change In 1967

"By now [1967, after 'Lucy In the Sky' was finished], it was evident
that John's personality was changing.  Instead of being opinionated
about everything, he was becoming complacent; in fact, he seemed quite
content to have someone else do his thinking for him, even when he was
working on one of his own songs.  By the spring of 1967, he was becoming
increasingly disengaged, and that would more or less continue until the
end of the Beatles' career."
-- Geoff Emerick, quoted from Here, There, and Everywhere
I've personally seen this happen to people too many times.  I've had
acquaintances fry their minds on dope and metamorphose into
Trump-mimicking Q-Anon freaks.  I had a neighbor go senile and start
boasting about his days in the Army battling the South Koreans.  I've
witnessed people joining cults and allowing fellow crackpots tell them
how to spend money and mistreat family members.