Was Crocodile stronger at Marineford? Or was he holding back in Alabasta?

 During the Alabasta arc, Crocodile displayed a level of power that was initially considered overwhelming by the Straw Hat Pirates. He possessed the Logia-type Devil Fruit called the Suna Suna no Mi (Sand-Sand Fruit), which granted him the ability to control and transform into sand. He had a reputation as a Shichibukai and controlled the desert kingdom of Alabasta from the shadows. His strength was showcased through his battles with Luffy and others. At Marineford, Crocodile was present as part of the war that took place at Marine Headquarters. While he did participate in the battle, he didn't display the same level of dominance as some other powerful characters present. This has led fans to speculate that he might not have been as strong as initially portrayed in Alabasta. It's important to note that power scaling and character abilities can be subject to interpretation and development by the author. Oda often keeps details deliberately open-ended to keep the story intriguing.

If spacetime is a fabric, what is it made of?

 Spacetime is not a physical object that is made of something. Rather, it is a mathematical concept that represents the relationship between space and time. In Einstein's theory of relativity, spacetime is a four-dimensional structure that includes both space and time, and it is used to describe the motion of objects and the effects of gravity.

The idea of spacetime as a fabric or a sheet comes from the fact that it can be thought of as a flexible, stretchable surface that can be bent and distorted by the presence of matter and energy. However, this is just an analogy and does not imply that spacetime is made of anything in the same way that a fabric is made of fibers or threads.

It's important to keep in mind that the concept of spacetime is purely a theoretical construct and is not directly observable. It is a way of understanding and describing the physical world, and it has been extremely successful in explaining a wide range of phenomena, including the orbits of planets, the behavior of light, and the properties of black holes.