Why has aluminium, rather than steel, prevailed in airliner construction?
You are right, on first sight it is actually surprising that aluminium prevailed. It comes with some disadvantages:


Crack growth must come first in this list. With only a small cyclic load, cracks in aluminium will relentlessly grow. This requires frequent checks and has caused many accidents. Fortunately for aluminium, this fact was only discovered after WW II when the lifetime of aluminium airframes shot up from dozens to thousands of hours, so aluminium was already firmly established as the premier structural material.
To connect two aluminium parts, only riveting or bolting are available. Recently, bonding has become viable, too. Steel offers a third choice in welding, which gives it the advantage in vehicle construction. Again, history gave aluminium a head start, because when the first metal airframes were designed, welding was still relatively little developed, so the restriction to riveting was not felt as the disadvantage it is.
Corrosion: Here it is generally better than steel, but far worse than stainless steel which would be the prime candidate (next to maraging steels) for airframes were aluminium not available. During the Berlin Airlift, salt or baking powder could only be transported by seaplanes because it would had permanently damaged the landplanes. Seaplanes used special, corrosion resistant alloys which were needed in the marine environment.


In the end, however, this is still outweighed by the principal advantage of aluminium: Its low density. This allows to use thicker gages for the same weight, so the buckling strength of aluminium skins is far better than that of equally heavy steel skins. In aviation, the demands of aerodynamics make the use of crimps or reinforcing seams impossible, and only the labor-intensive addition of closely spaced stiffeners could remedy this. Such a stiffened steel skin would still be inferior when it comes to hail damage or handling loads, though, so aluminium was the obvious first choice.

In order to keep material cost down, Junkers built his first metal aircraft from steel but had to switch to corrugated aluminium in order to make them light enough. Note that the structural integrity of his designs was ensured by a steel truss, and only the covering was from corrugated aluminium. Later stressed-skin designs did away with the steel truss.

To compare the strength and stiffness of different materials independent of their density, you can use their breaking length and specific modulus, which can be expressed as their strain length. Surprisingly, most structural metals have a comparable value and only composites can set themselves apart.

Despite its nasty failure characteristics, aluminium has defended its position as the dominant structural material: By the time composites were developed, the engineers and certification authorities had learned how to handle aluminium and had created a barrier to entry in the form of a host of tests and approved construction techniques which severely harmed composites. If all the materials we know today had been available a century ago, aluminium aircraft would had become an oddity, not the norm.