I mean, it’s one thing to fan remake a single player game from a decade ago in a very different way, and a very different thing to remake a live Multi-player game made in basically the same engine.

One of them (the Portal demake) used Nintendo’s proprietary code/libraries without permission, prompting a request to take it down, the TF thing ripped off Valve’s assets without permission and redistributed them, which got a DMCA. If you see this and think “Valve is out taking down everything they can like Nintendo” you really missed something.