From the Nobel Foundation:
At CERN, he became interested in the quark confinement problem. He could not understand why none of the expert theoreticians would embrace quantum field theories for quarks. When he asked them, why not just a pure Yang-Mills theory?, they said that field theories were inconsistent with what J.D. Bjorken had found out about scaling in the strong interactions. This puzzled him, because when he computed the scaling properties of Yang-Mills fields, they seemed to be just what one needs. He simply could not believe that no-one besides him knew how Yang-Mills theories scale. He mentioned his result verbally at a small conference at Marseille, in 1972. The only person who listened to what he said was Kurt Symanzik. He urged him to publish his result about scaling. “If you don't, someone else will", he warned. He ignored his sensible advice. He had also made a remark about scaling in his 1971 paper on massive Yang-Mills fields. No-one had taken notice.
"Gerardus 't Hooft: Biographical," Nobel Foundation (1999)
Nobel Laureate, Physics Prize, 1999