I notice everything is in metric this time
The hover crane is not unlike the Viking lander stage in many respects (lots of Viking technology is being recycled/built upon). I think, if everything is on target, key points in the descent profile are clearly the lowering of the rover to the surface (retrorockets based on those used by Viking) but also the supersonic parachute deploy (actually scaled up from Viking).
The parachute has to deploy at Mach 2 and has to quickly decelerate the vehicle to sub Mach 1.4 to try and avoid wild oscillations that will (have the effect of trying to) repeatedly open and close the 'chute envelope (and so dramatically reduce its efficacy). This is one of the most dangerous phases of the descent and one of the key problems with landing on Mars: there's a very narrow window of opportunity in terms of altitude and velocity because the Martian atmosphere is so thin meaning aero-braking isn't as effective so one has to deploy 'chutes at supersonic speeds. Obviously too early and your 'chute fails plus your downrange error can grow, too late and you risk ploughing into the surface. They're also making it harder for themselves as the ideal target touchdown location is about 1km above the (reference) Martian surface (areoid).
The early stage of the entry is interesting too. For the first time they will be flying a guided approach at hypersonic speeds, generating lift at very high speed in the upper atmosphere to both linger there in order to gain the altitude they seek at touchdown, and to minimise positional error at 'chute deploy (some tricks borrowed from Apollo command module entry profiles). The vehicle trajectory even climbs at one point. All previous entries at Mars have been ballistic, except Viking which was a full lift up trajectory (no guidance) in order to reach a high altitude landing site (but with corresponding loss of accuracy - they just wanted to get there and probably wanted to bleed off as much energy as high as possible to play safe anyway - 'chute deploy was at around Mach 1).
Then, of course, the backshell and heatshield have to separate cleanly! Not only does my mind boggle at all the opportunities for it to go wrong but it makes the Viking lander successes seem almost miraculous given what little was known, the approximations made at the time and limits of computer modelling in the mid 70's. Little wonder those landers were built like tanks.