Trump is oblivious to the fact that BRICS is now a bigger economy than the G7. The US is no longer an essential part of the global economy.
Increasing trade outside of the dollar is the only way countries can protect themselves from economic coercion by the US. In particular, China can obviously see that the US will go after them the same way they did with Russia. So, it would be suicide to agree to tie their global trade to the dollar.
Meanwhile, China also happens to be a bigger trade partner than the US for most of the world. So if it comes to choosing between the US and China, it's not really much of a choice. Especially given that China exports things people actually need, while the US barely has any manufacturing industry left accounting for less than 15% of the overall economy. The US is a big market, but it's not essential the way China is.
What Trump doesn't seem to get is that the hegemony of the US dollar depends upon people, well, trading in US dollars. Sanctions and tariffs are the fastest way to kill US dollar hegemony, so honestly I'm all for it.
I think he actually gets that part, hence why he's freaking out over countries moving off the dollar. What he doesn't get is that he can't just bully to get his way.
Historically the US would go to war or even coup countries to force them to trade with the US, it has spent a very long time building up its dollar hegemony. If it suddenly switches to cutting off trade with its largest trading partners, that will basically disappear overnight. It is already disappearing gradually because of US's obsessive use of sanctions has created a whole bloc of countries that have no choice but to figure out how to bypass the US dollar. I wouldn't even consider the US threatening to cut trade ties all its largest trading partners as "bullying," it really reflects how much weaker the US has become, because in the past it would just use force to enforce its hegemony over global trade, now it seems too weak to it is just threatening to throw a temper tantrum and threatening to pull out of the global market instead, despite this being something that will ultimately cause whatever is left of US hegemony to collapse overnight. I would bet a lot of money the US would not actually do this, Trump is just bluffing, because I'm sure he's surrounded by people who actually do care about maintaining US control.
If Biden has revealed anything about the office of the US presidency, it's that the president doesn't actually seem to control much of anything. The president can be a walking corpse and the state handlers will continue to follow the script.
So basically, great man theory is bunk
The problem US has is that the countries at the centre of BRICS are too big for them to take on.
It kind of reminds of a past job I had where a co-worker recently contacted me and told me he quit. The general manager was abusing his position and disrespectfully issuing out orders and demands to employees that already had 10 different things going on at the same time. The idea of not being a total hegemon just didn't seem to physically register in his brain and both of us ended up telling him to fuck off and leave him short staffed for Black Friday.