Tbf opposing gay marriage is quite an extreme opinion in much of the developed world. I suspect Eich's position on the matter is tied to his Roman Catholic faith, so although he showed a certain level of remorse in 2014, he never actually came out in support of gay marriage. He then later spread misinformation about mask-wearing during COVID, including suggestions that people could die from wearing a mask.
I don't think it's fair to call it "extreme". Small minority in some countries, minority in most and about half of the population in some is imo a fair assessment. Even in USA it looks more like 70-30 if I am reading the polls correctly.
Prop 8, the anti-gay-marriage proposition that Eich donated money to support, passed with 52% of the vote.
Eich never clarified his position (nor did he retract it nor apologize) so we have literally no idea what aspect of this he supported along with 52% of the population of California.