The new 2018 iPad Pro models have a number of weak points. Aside from the unrelated “Antenna Bendgate” saga, the two points that give most issue are where the very thin edges are structurally at their weakest. These points are principally at the centre of the long edge (where it is pierced for a microphone) and at the cutout for the USB-C port - where you appear to have a bend in yours.
Whilst you may have been careful to keep your iPad in a hard case, its design will influence how it is held within the case - and in turn, how you physically have to fit the iPad within its clutches...
If the case surrounds all the edges - and you have to apply some pressure on the iPad to seat it, you run the risk of applying pressure at a weak point. Similarly, if the fitted case is tightly fitting, it is possible that the iPad casing may be stressed, leading to mechanical failure. Both of these issues can, potentially, lead to bending of an already weakened iPad casing.
Whilst it doesn’t help you, the older iPad and iPad Pro models are much stronger. The minimalist design of the latest iPad removes material that might otherwise serve to mechanically strengthen the iPad casing. You’ll note that Apple’s own folio case is secured only with magnets - imparting no direct mechanical stress (and consequently no edge protection) to the iPad at all.
By all accounts the 2018 iPad Pro models appear to be, when compared with earlier generations, relatively fragile.