i think its because they have spent 8 weeks looking at their team and have probably not got a single player on offence outside of maybe trent taylor (as a 4t/5th receiving option) that will factor into the future of their team - so i think this is a case of them seeing if they can find parts around the league that will be a part of their offensive future
they cant have kirk cousins now but jimmy g can come in and play for them immediately almost like an audition and maybe keep them competitive because as much as the organisation will want the number 1/2 pick they also will not want to go 0-16
this move of course also does not eschew them from taking a qb in the top couple of picks either and if they decide to franchise tag jimmy g and have a 1st rounder play behind him they can do that for a year or have an open competition for a year - maybe even franchise him for 2 consecutive years if they want to bring in a 1st round qb too
they get to have a look at their potential qb of the future for another 9 weeks with privilege of first refusal on jimmy g this offseason - if he isnt their guy they let him leave in free agency and he gets a massive contract somewhere else and all they did was drop a high 2nd (depends on which 2nd rounder they give up) to a comp 3rd (which is nearly 2 rounds but is eased largely by the fact that they have another 2nd round pick)
and the best case of course is that he plays well and shows some things and they pay him franchise qb money and use their draft picks to put a load of offensive talent around him and let kyle shanahan build the offence he wants
