This is probably the last I'll post on the subject and I'll go back into obscurity for the next 5 years again, but to address a few of the responses...
If the owners wanted promotion at the start of the season and mowbray talked them down from that, then that's still on the owners. They're responsible for the strategy for the club and the target for the manager. That's a basic principle of business. People aren't responsible for what their goals are, they're responsible for achieving them (within reason). Whether they have input in what they are or not.
Also, with us getting so close to being a part of the playoff race up until the end of January and then capitulating up until April doesn't have an impact on the success of this season for me. The goalposts can't be moved and to judge mowbray on what could have been this season is unfair. If we had been in a relegation scrap and come out of the season 15th, it would have been a success and would have been seen as such by most people. To be basically safe by march is a greater success, just we're hardwired as humans to want progress. We're given 5 so we want 6.
As for whether mowbray can take us to the next level, ie the playoffs, which I believe will be the aim for next season, remains to be seen. I'm sceptical that he can in all truth. He needs to sort out a shockingly poor defensive record for a start. But, he has earnt the right to have a crack at it. He has done everything asked of him exceptionally well.
Put it this way, if your manager asked you to achieve x and you did, and even got beyond that and they turned around and said that because you got so close to y but didn't make it, they're letting you go... Would you think that was reasonable or not?