Are you under the impression that none of those people believed in God's existence and earnestly sought Him?:
"And without faith it is impossible to please God, because anyone who comes to him must believe that he exists and that he rewards those who earnestly seek him" (Heb.11:6).
Of course there were some people like that and they sure did not receive their reward in the lake of fire. Those who know that a God exists and revere Him and who live a life guided by their conscience are acceptable to Him, as Peter said here:
"I now realize how true it is that God does not show favoritism but accepts from every nation the one who fears him and does what is right" (Acts 10:34-35).
The LORD wants all of His creatures to be saved so He will not leave anyone without a way to be saved, as you imagine.