I went through that Barcelona one, and it must have been the weakest security I’ve ever seen.

Dude wasn’t even looking at the xray machine screen.

ICAO or whomever audits airport security would shit their pants if the Barcelona rail station had the same scrutiny.

I changed in Barcelona on my way to Madrid and went through this too, it seems like it's specific to Spain/Barcelona, at least for now.

Eurostar has had airport-style security for long time (maybe always?). Definitely 10+ years anyway.

This is partly to do with the fact that the UK was never part of the Schengen group of countries (i.e. countries where you can travel from one to the other without a passport), even when it was part of the EU.

I cannot say for Spain, but for the Eurostar it has been like that for quite a long time and it is related to the Schengen area border. The checks are made on boarding, so in Paris, Lille, London, Brussels, and Amsterdam before they started refurbishing the station (I am not sure about seasonal destinations but I can’t see how they could avoid checks at some point). It is not an example of increasing security theatre.

Spain has had train security even on long-distance domestic journeys at least since I lived there in 2008. I suspect it's a reaction to the train bombing they had, but don't quote me.