The program I just finished was/is a brick and mortar where almost everything is online. We were required to come to campus once a year for the first 3 Fall semesters for 3-5 days. Proposal defense could be over Skype. Actual defense had to be in person. It's a public university so while it wasn't cheap (roughly $12,000/year tuition & fees), it was much more reasonable than any private for profit.
I actually went BSN to PhD and was told it was possible to get done in 4 full years (attending 3 semesters a year). I managed to get out in 5 full years, almost on the nose. My first orientation was the last week of August 2014 and my defense was the last week of August 2019. I might could have finished 2 semesters earlier but there were health issues in my family but you know what? I've not met a single person who didn't encounter a major hurdle, personally, professionally, health-wise, or all of the above. . .
I honestly didn't know a couple of my committee members well at all but I had a stellar chair who personally recommended them and they were all top-notch.
What is the defense? Well, the dissertation is a long-winded written version of the research you will do in your last stage. I don't know if others do it differently but my defense consisted of somehow condensing that 38,000 word monster of a dissertation into a 25 slide/35 minute powerpoint presentation where I narrated the relevant parts of my research and findings. Then your committee (who has had your written dissertation in their possession for a few weeks), will question you, and you will "defend" your methods, analysis, and findings. If you have a good chair, you will be ready or he/she will not allow you to attempt the defense. My dissertation stage lasted about 4 semesters, with one of those semesters being when I kind of had to back away a few weeks due to family circumstances.