FYI, there is an ongoing network outage impacting CDN (Content Delivery Networks) Akamai especially as well as Level3 backbones, Cloudflare and other DNS providers that started yesterday and continues this morning. This might be messing with your downloads. Try setting DNS manually on the Mac to 8.8.8.8 and 8.8.4.4 while downloading the installer.
This Mac has a T2 security chip. Make sure you login to the Recovery Console and allow USB Booting with a local admin account.
If Catalina via USB worked then boot into Catallina and re-download Big Sur via Terminal
sudo softwareupdate --fetch-full-installer --full-installer-version 11.5
Then erase the USB flash drive and name it MyVolume and re-burn it via Terminal
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
Try running the installer via this method first. It will prompt to quit Terminal when it is ready to reboot.
sudo ./Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/startosinstall --agreetolicense --nointeraction
If that fails, try the USB installer again and completely erase everything from your internal disk with Disk Utility and allow the installer to create the volumes.
There will likely be firmware updates being made to the T2 and the Mac may appear completely turned OFF, it is not OFF it's writing to the T2 SoC and upgrading the BridgeOS. Do not interrupt it. It may reboot more than once.
If all else fails you may need a second Mac a Thunderbolt cable and Apple Configurator 2 on the second Mac to revive the T2 chip in the MacBook Pro 2019. Apple's very specific instructions on how to do this:
https://support.apple.com/guide/apple-configurator-2/revive-or-restore-an-intel-based-mac-apdebea5be51/mac
The USB-C charging cable is NOT a Thunderbolt data cable you will need a real Thunderbolt3/4 USB-C cable.