Apparently because these mini-PCs are even more overpriced (and what fools still buy them for this crazy money) than laptops and therefore their creators can buy wholesale quantities from AMD at an increased price, and laptop manufacturers do not want to pay as much as manufacturers miniPC, so they use Intel, which is apparently both more accessible and cheaper in large quantities.
Don't forget that AMD can't produce more than 1/5 of what Intel produces. And if they produce only 20% of the batches needed by the market, then the result is obvious - large laptop manufacturers will only work with Intel, because AMD cannot provide batches of the same size and at the same dumping price as Intel. And the larger the batches, the lower the cost.
This is a vicious circle created long ago by Intel, thanks to corruption in the US antitrust authority. If they had started to put pressure on them in time, AMD would not have found itself in a situation where it had no choice - in order to increase market share, it needs to dump large quantities, but then this is a minimum profit or even a loss, and AMD does not have that much cash in its accounts to win a price war with Intel, it will simply bankrupt them. If, of course, we assume that these are real competitors, and the fact that AMD has been an anti-monopoly gasket against Intel for many years...
Therefore, AMD is happy with the niche in the x86 market, but now it has become a burden for them, because there are more profitable markets where Intel has no influence or weight.
Therefore, it may happen that AMD will leave the x86 processor and SoC market altogether. Unless, of course, Intel, for the sake of providing cover from antimonopoly officials, will not secretly pour money into it again, so that AMD continues to pretend that the x86 market is still interested in it and creates the appearance that it is fighting Intel.