Who did (insofar as a generalized “who” referring to the human species) is relevant though. We know that humans a) exist, b) have means of transportation to travel the world and visit islands, and c) carve rocks into various shapes. That humans are the likely source of the carvings on Easter Island is a reasonable conclusion. If you think there is another species (including aliens) that could have made the carvings instead, then by all means present evidence to support the existence of said species and that they also have traversed the globe and have the means to produce rock carvings.
Otherwise your assertion is about as silly as wondering whether my house was built by humans, crafted by aliens, or conjured into existence by an inter-dimensional wizard.