What did Ethereum? Nothing, it has been lazy. 
The ATH of 2021 [$4,870] is still holding in 2025. 
Comparing Bitcoin with Ethereum is like comparing apples and oranges. Both are on different pedestals. Bitcoin always tops ETH. There's a reason there's industry is classified as Bitcoin and altcoins. However, I've my reservation about who's lazy. That expression doesn't accurately balance what's on ground but let's leave that argument for another time. The ATH of 2021 [$4,870] is still holding in 2025. I can’t remember a time when Bitcoin was truly outperformed by altcoins. And even if it happens temporarily, Bitcoin will always remain the boss or actually, not even the boss, but the king, since that title sounds more respectful.
That happened in 2021 with Yearn Finance (YFI) which achieved its ATH of $90,700+ in 2021, at a time when Bitcoin hadn't even got to $70,000.