Hitlers dislike for Carol is a very small side issue. Infrastructure is the main reason Romania got less than the other allies. Hungary and the Czechs bordered Germany proper and had many more miles of modern railroad, and paved roads. Shipping a trainload of equipment to Prague or Budapest was far less taxing than to send one to Bucharest. Some Romanian railways are even of different gauge.
Also the Romanians were not well regarded by the Germans. Whether they were great or not, I dont care. Also the Germans knew that machine tools and such shipped to Romania would be wasted. As stated Romania was a backward nation with a very low literacy rate, and no history of major heavy industries. Sending them much needed machine tools would only be a drop in the bucket towards the amount of infrastructure that would need to be built to support an infant Romanian armaments industry. They lacked modern factories, power plants(without which you have nothing), skilled workers, and everything else you need to produce war material. So as the Fuhrer, give me a reason why you would send Romania tools you desperately need yourself.
Romania was turned down in Fall/Winter of '39/'40 by the Czech's because all the Pz-38's were already reserved for Germany. Again, had Germany let Romania purchase many of the Pz-38's would Germany have won in France? What the hell good would they have done in Romania? Romania was allowed to purchase some of them from the Germans after the French campiagn, as many as the Germans could afford to lose. The Germans were always so hurting for equipment they couldnt afford to send the Romanians much, not because there was a vendetta.
Germany would invest in Romania's defence, with Werhmacht troops, not by supporting the Romanian regime.

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It's a sick, sick world. I'm a happy man.