They had to pay cash and transport the materials themselves
To destroy Germany's capacity to make war.
The signing of the tripartite pact helped interventionists get Congress to pass the Selective Service Act.
the war left behind destruction and bitterness in those nations
One thing Benito Mussolini did was outlaw political parties.
There were three main reasons:
1) They agreed politically with the Fascists (nationalists) and sought to make Spain their ally in Europe.
2) They wanted to test their latest advancements in military technology.
3) They wanted to test this equipment along with the strategies they had developed, to see how they worked in actual combat. The German and Italian "advisors" studied the tactics used and were able to train their own armies. Some German armed forces took part in the fighting, and Franco returned the favor by supplying a brigade of soldiers to the German Army during the battles with the Soviets in World War II.