GM offered DOHCs first that vastly out powered the imports and no one bought them. None of the issues with the Twincam would have been evident until they started hitting 80,000 miles and people neglected the timing belts, so it's only with hindsight that you even would have known an issue with the Twincam existed. Put them in a Chevy, and people bought the 3.1 pushrod. Put them in the the Cutlass and people bought the 4-cylinder or the 2.8 V6. Off the showroom floor Oldsmobile was selling a V6 that would perform with the SHO of the day without all the hype... and no one bought them.
GM offered DOHC in the Saturn LS series... it was roughly equal to the Camry and Accord outputs of the day... the cars even had dent resistant panels... and no one bought them. Most LS series Saturns are 4-cylinders
GM offered the 3.5 V6 in the Intrigue, still to this day one of the best W-bodies ever built, that Camry and Accord didn't exceed in power till nearly 6 years later..... and no one bought them.
People actively chose the 3800 or the 3400 over all these engines. Lesabre and 88 were the best selling full size family cars for years and years... even after Ford and Chrysler moved their full size offerings over to OHC or DOHC.
When given the choice, people chose the 3800 over any DOHC entry from GM. When they wanted a performer, they chose the S/C 3800.
It wasn't that GM wasn't offering DOHC... it's that the customers were picking the pushrods.... can you blame GM for keeping them in service so long? If the Lumina or Cutlass engine sales had been flipped to 80% DOHC v 20% Pushrod, as opposed to what happened in reality, we'd not be having this discussion today and the 3.6HF would be in it's 4th or 5th generation.
As far as getting there first, GM usually has... and then was ignored by the market.