Most tech bubbles develop that pretty quickly.
Admittedly, California has a little bit of that going for itself.
1) California is naturally aspirational, it's 'quirky' and the place that people have gone to 'escape' classical norms for a few centuries now.
2) The weather is amazing.
3) It's in the USA = a market big enough to support anything to start, before international expansion. Almost nowhere else can do that. Think Sweden: you have to go 'very international' and deal with many cultures/languages to get going.
4) Standford/Berkley - almost the perfect mix of both public and private ethos in the same spot. I'm not for or against either, but both systems have advantages. Also proximity to other pretty good schools.
5) SF artistic culture + VC culture + Tech culture - I would argue all are needed, and it just happened to be there before, and now they have a mass in all three. Granted, the art-vibe is dwindling.
6) Money - another thing that comes from both US scale and capitalist culture, that doesn't exist most other places. Rich people write big Angel cheques and take risks like few other places.
It's crazy to try to 'reproduce' the Valley elsewhere - it's best to focus on things that regions have as an advantage.
Canadians are not the most capitalist/lean-in people (I know this, I am one), and we don't fare well on R&D spending etc. But - the Oil Sands are almost unique to Canada, and developing around that are tons of relevant mini-innovations and side industries. (Eco-issues aside, but even then - some eco-innovations as well).
Montreal has a huge 'creative community' that they don't leverage well enough.
Sweden has a specific kind of culture that has lent well to their exports and innovations espcially in Music. They are a world powerhouse in pop-music ... Spotify should be no surprise.
When industries are related, or if there is a 'key advantage' somewhere in the core, then other, related inustries can leverage that.
'Critical masses' happens when there is some kind of relationship between the various companies.
Trying to 'just make startups' wherein there is no synergy between entities is not a good strategy.