That 'market share' isn't coming back. Crypto has diverged for good no matter how shitty or wobbly the different paths are. Different people are now doing different things under one very tenuous umbrella that should be abandoned. Anyone who didn't expect this is a silly sausage.
This is a good article on why "BTC domination %" on marketcap doesn't even matter:
https://medium.com/bitcoinfoundation/the-bitcoin-dominance-indicator-fallacy-2b11093869d4Yes it does. Market cap is a terrible indicator of Bitcoin's dominance, but in this particular case it's accurate enough to say that people now care about ETH and several other cryptocurrencies.
To use arguments like "name me one merchant that uses ETH. You can't.", is meaningless. Bitcoin has very few merchants relative to the total amount, and it wouldn't be so difficult for ETH to have that low-level adoption as well considering the amount of work that people are putting into it.
A limited supply of Bitcoin is not the same as a limited supply of gold. There are only so many scarce physical objects to use, but there are an unlimited number of cryptocurrencies that can be created, and cryptocurrency-related tokens (ETH). So I can't see anything continuously staying relevant unless it's
really deeply rooted in the world or it's superior to all alternatives in the eyes of the public.