What is the freehold point? Of course the Crown Estate own the freehold. The reason believe it or not is William the Conqueror. There are plenty of vacant properties so one seaside apartment isn't an issue. Property bought purely for investment is and a lack of council house building is too.
The housing situation is very complicated. People owning multiple homes is one part of a more complex problem
I guess two counts as multiple but it's really not complex. The council properties were sold off and not replaced and many are now in the hands of private landlords. Meanwhile some developers are happy to build luxury flats that are never occupied.
And you've seemingly given the Crown a free pass too
Along I assume with Lords who inherited their land because their ancestors were mates of William the Conqueror when he stole it in the first place.