Why didn't Nic Cage and Sean Bean just work together from the start?
Cage ended up stealing the Deceleration anyway, became a fugitive, and found the treasure all before Bean did. And unless I forgot, Bean, despite his shady background, initially wanted to examine the Declaration legally and didn't intend to keep all the treasure (that we know of), and he had powerful connections. So they either could've just let Bean find a way to convince people to examine the Deceleration (which I guess would be boring), or have Cage and Bean steal it together and return it when they found the treasure (which is more exciting for the plot).
The second choice might not seem heroic by Disney standards, but literally one year earlier they released a movie glorifying and romanticizing piracy, which then had 4 sequels as of this post, and is one of their most popular and successful franchises.