Gonna play a little devil's advocate here.
Think about it, you're an assistant that doesn't move up the ladder, and there are other opportunities out there for more money. Would you take them?
You're Sean McVay, doing everything it takes to maintain a winning team, and you have to micromanage a QB, be in his ear constantly before the play. The QB screws up, throws picks, takes sack fumbles, misses open receivers, throws behind others, hesitates to run on rollouts, can't handle pressure up the middle, has slow decision making, all several times during the season, with PFF's 3rd best offensive line. How frustrated could that make you? Imagine us as fans feeling it, complaining about it, making excuses for it. It's in concentrated form with McVay in the front row seat, knowing internally what he knows about the situation. And he gets to a point where blaming himself all the time is not going to instill confidence in his team that he's the proper leader. He and Goff are in their 4th seasons of winning with no SB trophy. There comes a point.
Now, imagine a veteran QB that doesn't need micromanaging, or constant tutoring if you will, being brought in to relieve McVay of that huge responsibility, allowing him to concentrate more on play calls and or/work on other things besides hand-holding. Yes communication with the QB is important, but how far does that need to go? McVay has tried to make it work on the younger player. Developed him to a point where he should be better and reach his potential.
Yes the Rams are obviously a playoff team, and they have some of the league's best players talent-wise. They should do so much more with the talent and skill that they have. Getting swept by an inferior heavily injured 9er team in the division 2x in a row is not an option. It's a situation that should not happen. Going up to Seattle for the division title and failing is taking a step backwards. What factors were holding this team back? Where was the killer instinct in these important games? Does it all fall on Goff. Not really, but he was a factor that made the decision to part with him a reality.
Now the way they did it, possibly not telling Goff, being sneaky, could be called callous, underhanded, deceiving, or worse. But what if the trade falls through? How will that effect Goff knowing his team doesn't want him but he's stuck there? How would that play out?
I'm just trying to see the overall picture. Being sneaky about talking to teams and not to the player happens in sports. There have been billions of trades that didn't happen, without the player involved fully knowing, or maybe just hearing possible rumors. The Lakers almost imploded in a pre-trade drama when their players learned their team wanted to trade them but were stuck there as the trade didn't happen.... before righting the ship and winning the title the next season. (after bringing in a proven star player, I might add)
When the sports trade is made, with all the sneakiness to try and prevent a blowup is involved, the GM and/or head coach will then call the player and pour on all the courteous outgoing accolades and respect as the player is heading out. Sure, all likely a smokescreen rather than telling the unwanted player that they lost confidence in them, but still respectful. That happens in sports all the time. (Good luck, we like you, but we don't want you in our future).
The situation in Detroit was different in that both Stafford and management agreed on the move with no ill will. There were many suitors for a player of Stafford's caliber. With Goff it wasn't as easy, as who would want to eat the bloated contract of a player who is not a top 10 quarterback. Who among us thought the Rams could so easily get rid of that heavy burden? It looked near impossible. The Rams had to gift other teams to take him. Expensive gifts. Here's your future, if you can help us fix ours.
No one is blowing up the team. Snead and McVay are constantly tweaking and trying to improve the team after SB and playoff failures. Sure they have made the mistakes of overpaying players and eating 1st rounders. They put themselves in the situation of not being able to keep players because of their salary cap issues with overpaid stars who failed to contribute based on what they were being paid. They made their bed and have had to sleep in it. They've obviously had to pay for their mistakes in lost millions and draft capita. But the Rams are still actively pursuing the goal to a title rather than merely sitting on the fact that McVay has 4 straight winning seasons and a 36-0 record when leading at halftime. They have not been the best team in the playoffs so far.
We'll see what kind of QB Goff is in Detroit without the fancy offense, the coach in his ear before every play, and most of all the talent. On the other hand, will he be relieved of the pressures McVay had on him and free to play with what he has inherently learned along with his natural talent on a mostly talentless team? He has to learn a new offense for starters. Develop his timing with new receivers. 1st round picks don't always work, they don't always contribute the first year. The Lions are only in phase one of a rebuild that could take a few years to even get to a winning season. It could be rough for Goff. And then what, does he get shipped to a third team? These instances are all in the cards. And the Rams are playing poker to win it all.