Self-fulfilling prophecy. Sharp's performances (and, almost certainly, the underlying data) suggested that his output and effectiveness was declining. You repeatedly criticise McBurnie's performances yet in the one stat which actually matters he thoroughly outperformed Sharp.
Sharp scored 2 goals in 38 appearances. 30 of those appearances were for more than 15 minutes and he was on the pitch for 1,462 minutes - 16.25 full 90s. A return of two goals (against 18th placed Huddersfield and 24th placed Wigan) at 0.12 goals/90 mins was not good enough for a player who first and foremost is a goalscorer. As you'd expect, his finishing was almost bang in line with expectation (footystats has him on 2.38xG or 0.15xG/90). McBurnie finished with 0.53 goals/90 minutes against 0.48 xg/90. He was getting more chances and crucially he was finishing them this season.
Billy can walk away with his head held high because he's played his part in getting us back to the Premier League but that remains probably the toughest league for a centre forward in world football. The defenders are quicker, stronger, taller and more intelligent than those in the second tier and if Sharp can't get the chances against Jake Cooper, Richard Wood or Liam Lindsay then he definitely isn't going to get them against Marc Guéhi, Rúben Dias, Issa Diop or Nayaf Aguerd.