He had years of work with Ebron, but Robert's was a back-up mostly blocking only TE, and might not have even been 2nd on the depth chart. Until this year. This year (actually stops right here and goes to check the beginning of season depth chart) Robert's is listed as #3 at TE. Most of Stafford practice went to Tate, Marvin Jones, and getting those guys ready. Then when they're gone or out hurt you have to get new guys like Ellington ready, and moving Riddick to the slot wr full time.
Every year we see amazingly talented rookies, and usually very high profile WR's going to new teams, and it is very rare for them to just step into a new place and work. Randy Moss in New England is one of the very few right away. But dont forget that he failed pretty miserably in Oakland. Chemistry comes slow.
Cooper Kupp
Calvin Ridley
DJ Moore (broke out vs the Lions)
Just 3 quick names off the top of my head who look great already. How much better would Golloday look on those three teams? All of Stafford's best WRs have been FAs - Tate and Jones. Nobody has ever come up under him. Look at Ebron now?? He's awesome.