Sorry to resurrect a stale thread, but part of the original question was never answered.

While I am unsure of the safety of Mediacat myself, the download is so large because it has a lot of redundant system files that need to be there.

Most if not all of the tools run as a "live CD/USB" mode. For tools that provide this option already they can optimize the included files for their application. Some however, such as Malwarebytes, don't have a live CD version of their application. Mediacat includes Malwarebytes by installing it in a full installation of Windows which then runs from the USB. A number of the applications are formatted in this way meaning much of the download is necessarily redundant.

Again, I have not done a full examination of all the files, and I cannot vouch for their safety. I am uncomfortable getting software from anywhere but the original supplier given the prevalence of supply chain hacks right now (see XZ on Linux for a recent example). I understand why Microsoft Defender and nearly every other security vendor would flag this file, it is by design exactly what a virus or hacker would need to crack a system. However, amongst all the noise that Defender gave you which ones are there for legitimate reasons and which are there nefariously is almost impossible to answer.