difficult to know for sure why Owlsley didn't go...maybe he didn't want to move again and they simply honoured that request. Just because you get traded to a contender doesn't mean you are going to start. What is the value of a 20 year old tender if he can't win the starting role from your already established winner.
Being here could end up being his best decision as he will face a ton of rubber to hone and continue to develop his, already, admirable skills. He must still be looking for an opportunity to play pro and sitting on the bench behind an already established starter on a contending team in your last eligible year may not work out that well for you (see Scotty Bowles).
Maybe management wanted to keep a guy who seems able to give your team a chance to win almost every night...even if your team is not, on paper, supposed to be able to compete with most of the teams in this league who are further along in their developmental "cycle". In the end, it is nice to have an above average tender as the last stand when you have a team at this level.
As for Carlson...I think you might have gotten a late round draft pick based on his performance this year and that makes it more sensible to keep him as an experienced vet to mentor the youth...IMO