Yeah, definitely weird! It's only Brave this sometimes happens with. It does not happen with Thunderbird, my EMail client.
Just out of curiosity, when Safari and Outlook 2019 open together, is that the "order" you quit those apps the last time you used that machine? That is, you quit Safari, launched and quit Outlook 2019 to re-check your EMail, and then shut the machine down? Myself, the first program I launch at startup (about 99% of the time) is Thunderbird, to check my EMail (once in a while I launch Quicken 2017 so that I can enter some transactions). I then launch Brave. After concluding my browsing activities, I quit Brave, and most of the time, I shut down the machine. Once in a while, though, especially if I've been using Brave for some time, I launch Thunderbird to re-check my EMail. I then quit it, and shut down the machine.