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.

How does Gondor maintain/rebuild its population after the devastating losses in the Kin-strife, Fourth Age and War of the Ring?

 In J.R.R. Tolkien's The Lord of the Rings, Gondor is a fictional kingdom located in Middle-earth. The population of Gondor suffers significant losses during several major conflicts, including the Kin-strife, the Fourth Age, and the War of the Ring. However, despite these losses, Gondor is able to maintain and rebuild its population over time.

One way that Gondor is able to rebuild its population is through immigration. In the aftermath of the Kin-strife, Gondor is able to attract immigrants from other parts of Middle-earth, including the kingdom of Arnor and the regions of Rhovanion and Dorwinion. These immigrants help to replenish Gondor's population and bring new cultural influences to the kingdom.

Another way that Gondor is able to rebuild its population is through natural population growth. After suffering losses in the Kin-strife and the Fourth Age, Gondor's population begins to grow again, as people have children and families and the population increases.

Finally, Gondor is able to rebuild its population through a combination of immigration and natural growth, as well as through the rebuilding of infrastructure and the expansion of agriculture and trade. These factors help to create a more favorable environment for population growth and allow Gondor to recover from the losses it suffered during the Kin-strife, the Fourth Age, and the War of the Ring.