Supposedly because at the time of the acquisition, "Canyon Bridge was licensed and regulated by US law." but "Since then it has moved its headquarters to the Cayman Islands and as such is no longer a US-controlled entity." [1]. Although that sounds pretty flimsy. I suspect, given it happened in 2017, it was judged politically unwise to block a Chinese state investor when the UK was looking to increase global trade post-Brexit.

Eventually it seems the UK gov woke up and blocked a Chinese attempt to take over the board and move the company to China[2]. Now it seems there's a plan to IPO again in London or Nasdaq[3] so the Chinese owners can exit.

[1] https://www.bbc.co.uk/news/business-52275201 [2] https://www.ft.com/content/654a6d68-ef26-47b2-9da5-9029c570f... [3] https://www.ft.com/content/e0c48d30-866d-4efd-9d78-21e49d366...

As we've seen with Russian money and influence over London... the UK government couldn't care less where their IP goes.

IMG wasn't considered important enough to be a strategic asset unlike ARM. Remember IMG was on the verge of bankruptcy or collapse. Apple, representing 70% of their revenue will somehow no longer be paying them a single penny. They had lots of baggage that were not part of Graphics IP from Wireless, MIPS, to IoT.

ARM had Mali. So on the surface UK isn't really losing any strategic asset.

And you have to remember, this was in 2016 / 2017. The world still doesn't know a damn thing about China. ( or may be they do but they turned a blind eye to it )

None whatsoever - they don't care.