it was well known that Smith was generally not accomodating of rookies. Theory was that he didn't like helping develop guys who could eventually replace him. Others said he was just surly (all speculation, of course).
As to Colbert, in his first season he set the records for Panthers rookie receivers that remained up till now. that's what his tweet is all about.
The year after that, it was like he just forgot everything about how to play football. And eventually, he was gone.
It does lend itself pretty well to conspiracy theories.
Are they valid? No idea.
Colbert, of course, broke the rookie records while Smith was hurt. And did nothing of worth after. So there's something to that.