Is BPH caused by poor hygiene around the genitals? Is BPH just nonbacterial prostatitis?

No. No to both questions. BPH is benign prostate hypertrophy. In BPH the prostate gets bigger and when symptomatic the urine stream changes, the bladder doesn't empty as well and one has to go more often to keep up with poor bladder emptying.
No. BPH is not cause by poor hygeine or inflammation.It is a fibro-adeno-myoma. In simple layman terms it would be fair to call it a"benign growth" of the gland.