First of all, geographically, Lanzhou is located along the Yellow River and belongs to a small basin topography, which is easy to defend but difficult to attack. Strategically speaking, Lanzhou guards the four directions of east, west, north and south, and is close to the front line in the west, so it can flexibly support the front line. Inner Gansu is located closer to the mainland, which is convenient for the central government to better control. Zhangye is almost at the front line, and it is too dangerous to be the provincial capital. Once it falls, it is likely to cede the whole of Gansu.
Secondly, foreign invasion was serious at that time. The northwest Zhungeer is eyeing up, and people familiar with the history of Qing Dynasty know that Zhungeer was a menace to the Qing Dynasty in the early Qing Dynasty, and almost all the means such as marriage, war and trade were used in the Qianlong period. Therefore, Gansu must choose a city that can attack, retreat and defend, and insist on fighting with Geer at the front line, so Lanzhou naturally becomes the first choice.
Finally, it was because the Qing government was worried about Shaanxi. After the Qing dynasty entered the customs, it was found that the folk customs in Shaanxi were difficult to control, so on the one hand, it chose to appease the people and try to let Han Chinese officials deal with internal contradictions in Shaanxi. On the other hand, the Qing government is also considering how to divide Shaanxi for better control, so the natural geographical advantage of Gansu close to Shaanxi makes the Qing government think that it can form a better restriction on Shaanxi Province, so Gansu's choice is partly due to this reason.
Therefore, the choice of Gansu has considered many factors comprehensively, and now it is also a good choice for the development of Gansu.