NP-hard proof with reduction from two known NP-hard problems
If you can reduce one NP-hard problem to a problem&nbsp;$L$, then $L$&nbsp;is NP-hard. If you can reduce a second NP-hard problem to&nbsp;$L$, then so what? You already know that $L$&nbsp;is NP-hard. How could reducing more problems to&nbsp;$L$ make $L$ easier (e.g., not NP-hard)?

It's like saying, "If I have one million dollars, I'm rich. If I have two million dollars, am I still rich?"