The short answer is during the Second World War. As the war progressed it became clear that tanks needed to be balanced between speed, armour, and firepower​. Using some examples from British tank development we can see this process unfold.

British tank doctrine at the start of the war was based on the concept of Infantry​ tanks, and Cavalry tanks. The former were slower vehicles designed to support infantry advances, the latter designed as breakthrough tanks. The Infantry tanks were heavily armoured, slow moving vehicles whilst the Cavalry tanks were quicker and lightly armoured. This design philosophy was followed for the early years of the war resulting in the Churchill and Comet tanks as the last examples of Infantry and Cavalry tanks respectively. Futhermore, some designers, keen to develop vehicles to capable of breaking through trenches harked back to the First World War resulting in the TOG II*. However, by the mid point of the war, design specifications led to the development of the Centurion mk.1, widely recognised as the first main battle tank although it was designated as a heavy cruiser showing how tanks came to be designed to fill two roles. Although in development from 1943 the Centurion didn't see active service in the Second World War, it saw a lot of action throughout the second half of the Twentieth century.

So how does this relate to the Ratte and FCM F1? As is hopefully clear during the war design principles changed and tended towards medium tanks or MBTs, capable of manoeuvring, providing fire support, and engaging other tanks. The super heavy tanks were designed to take little damage whilst approaching an fixed defensive line. Owing to their limited usefulness the need for these vehicles was not sufficient for resources to be allocated to their production.