I dunno I cant see how people with those jobs easily gained the ability to get that much property simply. However timing may have made a big difference.
Why for example did they get 3. Suspect at some point they had funds available to double up.
My grandparents, served as youngsters in WW2, when they married sometime after the war they couldn't afford a house they had to rent a room, and thats with my grandfather in the police by that point. I know my nan worked but forget what, I think shop but not sure.
My parents managed to afford a decentish house, but gained quickly in the 80s, my father an accountant and my mother part time (full time mum she would say). They skimped on many things, I for example had crap clothes/trainers when I went to secondary school, most of the "poor" kids had better gear than me, whilst we lived in a highly desirable area.
I didn't struggle as such to buy, first property right at the start of the 90s. In fact I would argue from everything I was told by both my parents and grandparents I probably had it easier. I think by then wages were better. I did have a pretty decent job (accountant) and my other half also had a decent office job. It wasnt easy, and this is my point, its never been really cheap, like no need to worry about money cheap to buy a house. What was easier to manage was that the house prices were cheap, but the rates high. As the rates started to come down, and house prices went up then the affordability for those already bought in get better really quickly, when you have highish inflation driving highish wage rises once your on the ladder its great.
People forget lots of things in regards mortgages as well, and the general state of housing and space etc.
60s etc land was cheap, and as such there was no real pressure to maximise density in fact there were no density plans. Whilst people blame developers for smaller houses its the councils that devise the density plans! So there was more land available for fewer houses.
Nimbyism wasn't really a thing
You couldnt just apply to a bank for a mortgage. Banks mainly didnt do mortgages, and so you were forced to use a building society, and they wanted to see far more evidence of good financial management, like for example having a good savings history WITH THEM.
Capital was often limited, my father tells me of when he would que round the building society on the day they released funds in order to secure a mortgage, once the allocation was done thats it. "Come back next month folks"
Cities, towns etc were smaller. So everyone was closer to stations etc, public transport worked (somewhat) so it was far easier to get around without a car, and people tended to work closer to home, less commuting costs.
I knew a girl at work in the early 90s. She was struggling to pay her mortgage, she stopped eating. I think many who never saw it think it was different somehow.
Things like "At 10:30 am on 16 September, the British government announced an increase in the
base interest rate, from an already high 10%, to 12% to tempt speculators to buy pounds" happened.
A simple solution to start addressing the issues would be to start getting the public on board to much more land being used for housing, until you do that you have no hope.
The housing would probably feel a hell of a lot better value for money if more space was allocated, the costs of adding an extra couple of metres in each direction when building isnt that high since a big chunk is fixed costs. Kitchen, bathroom, staircase, heating system etc etc