This is an interesting question, but in reality saying that the treaty of Versailles was lenient isn't really correct.

The reasons why most historians, and even germans at the time, thought that the treaty was too strict are many:

1 Territory-wise the germans had Alsace-Lorraine, Eupen and Malmedy, Northern Schleswig, Hultschin, West Prussia, Posen and Upper Silesia taken away from them and given to France, Belgium, Denmark, Czechoslovakia and Poland (Saar, Danzig and Memel were put under the control of the League of Nations and the people of these regions had to vote whether they wanted to stay in Germany or not in a future referendum).

2 Militarily the Germans saw their army reduced to 100,000 men and deprived of all tanks, and the German Navy was only allowed to have 6 ships.

3 Economically Germany was forced to pay massive war reparations and without some of the territories they lost that were very important for the german economy the country was on the verge of bankrupcy.

4 Last but not least, clause 231 (aka the war guilt clause), made Germany acknowledge that she effectively started the war, thereby taking the blame for all that happened.

This was enought to humiliate the Germans and to make them hold a grudge against the Entente powers, and this grudge would eventually help lead to WW2, since Hitler counted on this treaty to rile up german citizens.

So basically saying that the Versailles treaty was lenient is a bit of a long shot, since it was a very unfair treaty designed to not only cripple the german economy but also the german people's morale and pride, so even though this treaty was trying to prevent another World War it ended up hastening the process of WW2.

TL;DR There are many military and economic conditions that were in the treaty that not only weren't lenient, but were also downright unfair and too strict. Although this treaty aimed to prevent another World War by crippling Germany, the country that was seen as the most responsible for WW1, it ended up giving people like Hitler another reason to start a War.

Source: All hell let loose, Max Hastings; The First World War, Hew Strachan.

Edit 1: I clarified some things and did a grammar check!