Because fuck the swamp first of all. Second of all the sailing across the sea and running the boat was much more efficient than running 19 scrap at a time across the perma wet swamp with Draugurs shooting at you and Oozes leap on you. It sounds like it was more complicated, but we'd just take a boat and portal pieces over. Drop it on top of the crypts (only oozes could get up there) go mine iron, dump it in boat, take portal, repair shit, come back, repeat. When storage was full we just sailed back and unloaded onto our wagon and had the smelters ready to go. The sailing was probably a 3-5 minute excursion each way, which is like manually running back and forth to the swamp twice.
We ended up with essnentially 3 FOBs. A main one next to the trophies and starting point. This housed all our portals and upgraded forges/workbenches/agriculture. Then we had one in a black forest biome early on for copper/tin smelting that also had smelters/forges. Then we made one in the plains on the border of a swamp/plains/black forest/water that had full forges, workbenches, smelters, kilns, and blast furnaces. That's where we did all the high end crafting for T5 stuff which required needles and fine wood etc etc from the Plains. We actually made the base IN the black forest so you get easier raids (trolls, skeletons) rather than Plains raids like goblins.
With 10 people we had to have a few bases or else all 8-10 people were in the same place lagging the fuck out of everything and interacting with the same shit at the same time. This way we usually had 3-4 at main base organizing/crafting 2-3 out gathering wood/food and 2-3 out gathering ore and 2ish out fighting goblins, deathsquitos, drakes, etc..
This is definitely a game for 4-5 people. 8+ people it becomes a laggy desync fest, especially in tight quarters. Also upgrading every tier of tool/weapon/armor for 10 people is much, much more daunting a task for a large group. I think it came to like 72 iron per piece of fully upgrade T5 armor. That's a lot of grey cheddar.