I didn't watch ENT in the original run, so probably I'm talking about something that was already discussed/explained 10 years ago. WTF the Xindi sent the beta version of their weapon to Earth? Scratching Florida did absolutely nothing to reduce Earth's space-military capacity and, most relevant, alerted their enemy of their intentions prompting Archer's expedition. Note that Earth didn't know anything about the Xindi before the attack and so they could have developed the weapon with all tranquility. The other beta version they made, they tested in a uninhabited planetoid nobody cared about --- and inside their territory.
They also didn't know anything about the Xindi after the attack. Earth only found out about the Xindi because Future Guy told Archer about them. And the Xindi obviously couldn't know he'd do that. If FG hadn't said anything, nobody would have ever heard of the Xindi, let alone found out they were behind the attack.
The prototype weapon was sent to change the future for the Sphere Builders. They were presently involved in a war with Earth and Starfleet during the 27th Century. They decided to use the Xindi to attack Earth in order to disrupt the timeline. The attack on FL changed the outcome of the war slightly, and allowed the Sphere Builders to keep fighting.
But what part of the Xindi attack told Earth where to send that expedition? It's a big galaxy, and nothing from the attack (body and wreckage) suggested where to find the Xindi. Now here's a question, why didn't future guy or Danials tell Earth (through Archer) about the attack in advance?
While I enjoyed the show. I can't say I ever thought it was ever well written or acted. It was closer to Andromeda/Final Conflict than TNG/DS9 to me.
Which they wouldn't have had a single clue what to DO with, without Future Guy's information. They wouldn't know that the body was a Xindi, where it was from, what its race's ultimate intentions were, or anything like that.