There was a weird pattern back then. A team would be kind of middle of the pack in the regular season and go on to win the championship. next season, they'd dominate but fail to win it. Two-peats didn't happen. I think this was true of Portland, Washington, Golden State, and Seattle.
Thompson was taken with the 1st pick in the 1st round by a team that won the championship a couple seasons prior.
Looking at the roster his rookie season, there were pretty good players. Ron Brewer was a stud in college and a rookie that year. Hollins, Twardzik, Lucas, TR Dunn, Steele, Gross, and Tom Owens. In fact, Owen was so good he must have forced Dr. Jack to play Thompson at PF.