Has there really been a housing boom?

The answer is no. There has been a boom all right, but it has been a land price boom. This is not semantics - the fact there was no housing boom has a stark implication: society does not need to move resources away from construction in the long-run as has been suggested or assumed time and again (see for example this related discussion). We - meaning most of the western world - have not been building too much.

Development is generally severely constrained by the planning system,  so the returns to developing land to the landlord are way above normal. Unless the price of housing falls below construction costs (impossible in Europe, extremely unlikely in most of the metropolitan US), landowners that offer their land for development will keep enjoying a pure windfall gain, albeit one that is smaller the lower
house prices go. The point is that whether the windfall gain is small or large is irrelevant; in both cases there's profit to be made (and societal gains to be reaped) by developing the land. Keep in mind that agricultural land (the alternative use) is next to worthless - in the UK it's £7k/hectare on average, and this is probably amongst the most expensive in the world - while land carrying planning permission is worth more than 15 times that.

The reason you don't see development now is that landowners are holding back for higher prices in the future - it is fundamentally a short-term thing. If expectations about future prices adjust, there will be a renewed supply of land offered up for development. Unless land prices reach zero, no resources should move away from construction in the long-run.

Henry George's thinking on optimal taxation is also related to this observation.