yeah looking at the lowpoly, how straight the lines appear. i assume they built the lowpoly first, then used it to create the highpoly, not sure if it was actually sculpted or maybe just smoothed, baked and all surface detail is just done in a software like substance painter.
Make a box, convert to poly, make some cuts, push vertices to closer represent final form. Repeat cuts and moves until you satisfied with how it looks. Sculpt over it for fine detail. Bake to lowpoly.
Try what myself? To model this? Piece of cake. Checking the model structure I told you how I assume it was done. Might be highpoly first but the very straight lines make me think this was modelled not done with retopo. Learn how to model and you can create this lowpoly easily. Converting it to a sculptable mesh is not…