Technical questions Malware and Microsoft Defender for Windows 10

Why did my Microsoft Defender detect a malicious file in AppData\Roaming\Secure\QtWebKit4.dll (Trojan:Win32/Wacatac.C!ml) during a full scan and the Kaspersky Free and Malwarebytes Free scans didn't detect it?

Was it maliciously modifying, corrupting, or deleting various files on my PC before detection? I sent it to Virus Total, the hash: 935cd9070679168cfcea6aea40d68294ae5f44c551cee971e69dc32f0d7ce14b

Inside the same folder as this DLL, there's another folder with a suspicious file, Caller.exe. I sent it to Virus Total, and only one detection from 72 antivirus programs was found, with the name TrojanPSW.Rhadamanthys.

VT hash: d2251490ca5bd67e63ea52a65bbff8823f2012f417ad0bd073366c02aa0b3828