Well antitrust is basically what stopped the deal from happening [1]. If they had gone through with the deal and done this strategy I imagine it would have been a slow 5-10 year shift, not an immediate action.

> The main concern among regulators was that Nvidia, after the transaction, would have the ability and incentives to restrict access to its rivals to Arm´s technology, which would eventually lead to higher prices, less choice and reduced innovation. [2]

[1]: https://www.ftc.gov/legal-library/browse/cases-proceedings/2...

[2]: https://www.pymnts.com/news/regulation/2022/collapse-of-nvid...