> It seems to me that the Raspberry Foundation chose the Broadcom SOC
> of the Pi because it used the Videocore VI (Pi 4/400) or Videocore VII
> (Pi 5) which is documented and for which there is an Open Source driver.

The original decision to use the BCM2835 was more despite of the VideoCore IV than because of it. Broadcom delivered the SoCs at cost, and Raspberry Pi Foundation's Eben Upton had previously worked at Broadcom's VideoCore development team. The VideoCore GPU drivers only became fully open source a while after the release of the first Raspberry Pi.

https://www.theregister.com/2012/10/24/raspberry_pi_broadcom_soc_drivers_now_fully_open_source/