I mean another guy will just end up probably uniting the Hawaiian islands anyway. I mean it was pretty much in my full opinion inevitable.
The trend towards unity had been building up for a while before Kamehameha, that's true. However, changing the conditions of unification will have major knock-on effects on Hawaii's fate post-unification.
For example, the islands may still be disunited when the initial Christian missionaries come, and they could end up allying with a chief who ends up losing a war of conquest. The conquering kingdom decides that all the elite of this new kingdom, including foreign advisors, must be executed. Killing missionaries could be a causus belli for Britain to conquer the islands, a century before they were annexed by the US IOTL.
Alternatively, perhaps the missionaries are just exiled. Hawaii is left alone while unification wars rage for another decade or so, and come back-but different missionaries, once again, makes a different fate. IOTL the first missionaries to Hawaii were Protestant missionary families from Anglo backgrounds, whose children formed the basis for Hawaii's planter class. ITTL, French Catholic missionaries might take their chance and come in, converting the Hawaiian elite to Catholicism and setting the groundwork for later French annexation of the islands as per Tahiti.
Or, perhaps France's political instability means that they aren't able to annex the islands ITTL, and the US or Britain makes Catholic Hawaii a protectorate. ITTL the (officially) chaste Catholic missionaries have not created the Capitalist planter class, and there are no enormous, island-spanning plantations taking away water and land from Native Hawaiian farmers and drawing in immigrants. Francophone British Protectorate Hawaii (hey, a similar thing happened IOTL with Mauritius) comes into the 20th century with a majority Native Hawaiian population, and a landscape that still consists mostly of small-scale terrace farms and fishponds instead of industrial plantations and artificial sand beaches.
