Greenwood hasn't had injuries really and we only have 2 main attackers as he only just broke through to be a starter. Again, injuries will happen. Rashford was obviously overplayed. Martial had a 2 month hamstring right at the start of the season in August, and then nothing for the rest of the season. Nothing to do with being overplayed, just probably wasn't ready for the start of the season. Getting Dembele (or anyone) means we don't need to overplay the front 3. Thats the goal. Rashford wouldn't have been overplayed if Greenwood was more ready AND we had another top attacker who is versatile. You drop Dembele into the rotation, or Sancho, and then you have 4 players fighting for 3 positions, with Dan James and Ighalo as further backup for Carabao cup. Most of the year we had Rashford, Martial, a newly turned 18 year old and then Dan James who just came from the championship as our only attacking options. Pogba was injured and we had no backup which meant player quality was really low. Add Bruno, and we're less reliant on the 2 star players in attack we had. Pogba fit again aids that.
Add another top attacker in the rotation and Ole won't have to overplay, which means less injuries for all, better bench options, better competition for places leading to better performances. Its a no brainer to get in a versatile but mainly right sided player, who is a similar level to Martial/Rashford/Greenwood. Sancho is the dream, but looking like its not happening now so on to the next. Dembele is the next best option and still a brilliant option. The injuries are a risk, but in no way is 2 injuries before the age of 23 a sign of things to come and something irreparable. Needs to be managed back to full fitness, and just get back to normal. Giggs and Messi both had constant muscular injuries in their young days, eventually they got over them and barely ever got any injuries. Its not like its repeated knee injuries like Hargreaves.