What has changed that has allowed him to take off? Is it the coach?

Coach and he's moved over to center.

Tage against the machine

Tage actually started to display his offensive skills playing for Rochester over two seasons 2018-2020 with 12 goals in 24 games, plus 2 goals in 3 playoff games.
He was hurt in the only game he played for the Sabres in 2019 and missed the entire season.
That year and the following year, Krueger messed nearly every player on the team and his play suffered.
Granato became the coach near the end of last season and Tage finished with7 goals and 12 points over his last 23 games.
There is a bit of luck associated with this season as his shooting % is nearly double his career average.
But I am not surprised as I know it takes longer for big players to develop.
I suspect if he continues to perform he will finish with over 20 goals and around 50 pts.
Cozens may need another year as he is only 20 years old but he may very well reach the 20 goal mark this year.
Mittelstadt could be the best of the three IMO, it is a shame that he was hurt in the first game of the season.
The future looks very bright, it is a shame that Murray set back the rebuild by 8 or 9 years.
While he missed on Draisaitl taking Reinhart and Sergachev taking Nylander, he did well taking Asplund, Bryson, Borgen and Olofsson in the later rounds.
He was giving away draft picks faster than I pass out Halloween candy.

SDA is not a throw in prospect he is killing it in the AHL rn you won’t get him as a sweetener