Merchants don't adopt Bitcoin because their clients don't use it. Clients don't adopt it because merchants don't support it, and people want to have a payment method that can be used anywhere they go. How can this vicious circle be broken? Who will make the first move?
And by adopt I mean adopt for payments, not hodl it as an investment.
I think we are already seeing this cycle being broken, before the pandemic businesses did not felt the need to adopt bitcoin as the economy was going well, now that things are not as clear they need to get all the money they can to keep their operations profitable, so some merchants are already accepting bitcoin on their businesses, even if right now this does not bring a lot of profit it is better than nothing, and they think they can get a bigger share of that market in the future as people will prefer to spend their money on businesses in which they have being spending their money for some time, so they see this as an investment that will pay even bigger dividends in the future.