A president simply cannot order his party to do a thing, they never have that much sway over their party.
You clearly haven't been paying attention mate, Trump can and do order his party around. He killed a bill Republicans themselves worked on with just one tweet because it would've gone against one of his narratives against Biden and he wasn't even the president then. Republicans either fall in line or get ousted, it has happened multiple times just in 2025. Trump presidency doesn't confirm to norms of the US, it is far more like how our government operates. Both legislative and judicial bodies virtually handed all their power over to him already.
Only if democrats win in 2026 and 2028 this will change, but I really wouldn't bet on it because people behind Trump play dirty and far smarter than him.