Unix also predates DOS/Windows and as I said, Unix uses a single control character for both functions (carriage return IIRC).
Unix (including MacOS since version 10, but not Apple's earlier OS) marks newlines with just a line feed character, as I said above.
Why MS had to make DOS/Window different on this I have no idea.
It wasn't a matter of Microsoft making DOS "different". There wasn't a real standard for them to comply to in those early days. Or, rather, there were many conflicting standards for Microsoft to choose from, and the one they chose happened to be different from the ones that other systems that survived the '80s chose.
Unix used just a line feed. Apple, the TRS-80, and the early Commodore machines used just a carriage return. IBM (for whom Microsoft originally produced DOS) used on their big iron a completely different character set (EBCDIC) that had a newline character that combined both functions. Atari systems also used a different character set with a single newline character. The various CP/M systems (and there were a bunch that you don't hear anything about anymore) used the CR/LF combination, and that's the convention that DOS adopted.