Yes, you're correct.
It was caused by a completely beaten down immune system from the lifestyle choices of gay men in the late 70s nightclub scene:  unprotected sex with multiple partners, syphilis (bacterium), alcohol and drug abuse.  There was no virus involved.  You couldn't 'catch it' as they'd have us believe.  These men simply needed to stop the abuse to their bodies, eat some healthy food, get some rest, and clear up their STDs.  This is done very inexpensively.