The issue is that these companies were doing really well, got acquired as a result, but then mostly shrivelled to nothing. Let's hope ARM doesn't get cursed that way...
Well, no, they weren't. With the exception of ARM that genuinely is doing very well, quite a few of the others sold out because they weren't doing well. In the case of SwiftKey it sounds like they were losing money and decided to double down on it by giving it away for free and then charging for things nobody cared about!
SwiftKey's problem is that they had a tiny window of time after inventing it where they could have charged lots of money to power users before the Android team just included their invention in the core product. Apparently they were unable to capitalise on that time and ended up selling to Microsoft who now gets to fund their loss-making product. Although I loved SwiftKey as a product, business wise I'm not sure that's a loss for the UK.
SwiftKey's problem is that they had a tiny window of time after inventing it where they could have charged lots of money to power users before the Android team just included their invention in the core product. Apparently they were unable to capitalise on that time and ended up selling to Microsoft who now gets to fund their loss-making product. Although I loved SwiftKey as a product, business wise I'm not sure that's a loss for the UK.