Europe is most certainly not doing this. Trump isn't even serious, he's just "telling them to stop" in order to aid European anti-Trump propaganda which is used in Europe ironically to support US interests. Trump doesn't care that diesel is going up, especially because his friends are selling it. Cutting off Russian ability to join in this smorgasbord by causing a local diesel shortage for them also cuts off any concern he could possibly have about diesel prices.

Notice that he didn't end US diesel exports, he entertained the idea.

If Europe thinks they're "in this alone," and Europe is the "only one left" who will "defend" Ukraine, then Europe has to rearm in fear and figure out how to send more support to Ukraine, like to cut social services and ignore their heat/power bills to do it (and to steal from Russian accounts, which is being debated again.)

They will buy the weapons from the US, they will shore up the Ukraine war for the US, the will buy more LNG from the US, they will destroy local anti-US politicians for the US in favor of NATO, all to own Trump. Remember, Trump "hates" NATO. Not that he doesn't support everything they're doing, he's just threatened to stop paying for it i.e. they'll serve us for free. He's going to build a Ukraine War, and Europe's going to pay for it.

As a tactic, it was obvious why the US/Ukraine had to be aggressive right now; not only is Russia doing exceedingly well financially due to what the dumb Iran War did to prices, but winter is coming. For Ukraine, they were convinced that this was their last chance to make an impact before they were frozen. For the US it was an opportunity to burn weapons (so we can grab US taxes to make more), to get Russia to stop exports (because LNG goes up in Europe, and US oil goes up in general) and lastly and maybe most importantly to raise political support in Russia for strikes to civilian infrastructure. Putin is the conservative in Russia, and the politicians who are against him are demanding that he escalate rather than continue to bleed Russian lives forever.

If the US can convince Russia, who has been very gentle with Ukrainian civilian infrastructure, to destroy Ukrainian power going into the winter, the misery and death that will hit Ukrainians will be talked about for the next century (barring an big warming effect of the extreme El Niño.) That might fire up Europe even more into a delusionally belligerent frenzy (European NATO elites are losing the population), and possibly shore up support for more spending on Ukraine in the US itself. The US has suffered through a distinct lack of Russian atrocities in Ukraine, and this would be a great time to get some.