Why did the Silence predict that silene will fall in a victorious tone of voice?

Why did they build a makeshift TARDIS?

Why were they influencing humanity?

Why did they blow up the TARDIS (confirmed by Moffat I think)?

Why did they build an astronaut suit?

Also why did they want to get to the moon?

1) They're villains. They aren't going to be half-hearted about their ambitions for victory!
2) Apparently they're all over the world. Last season the doctor only speculated that the ship was a primitive copy of a TARDIS; as such he was probably just saying it was a spaceship perhaps capable of time travel.
3) They're parasites. They don't create themselves, they take humanities resources using post-hypnotic suggestion to survive.
4) Who knows... If u watch the big bang, the voice that says "silence will fall" doesn't sound that much like a silent: it's a raspy angry voice, and it's not electronically phlanged and lowered I'n pitch like the silent we have seen this series... Maybe it wasn't a silent?? (who knows!)
5) to protect the child. Apparently the child will "bring the silence" somehow as they told Amy they "did her honour" for her part. And it's pretty clear from the ep that the girl is amys child (the pics in the orphanage. Who knows how tho! (perhaps the child is such a huge paradox that it will allow them to destroy the universe again... Who knows!!

Also they didn't want to go to the moon. They planted the suggestion just so humanity would create a space suit to act as a life support exoskeleton for the child, in order to protect it.

I thought the phrase Silence Will Fall refers to their downfall.

It was confirmed on Confidential that it was a Silent. They probably decided on a change of voice by series 6, or maybe they have variable voices.

Ah thanks. I don't watch confidential! I don't think that silence will fall means their downfall though... "Silence will fall" is a phrase, fall in this context I think means that their "silence" will fall over the world/universe.

Oh yeah, you mean the silence that fell at the end of The Pandorica Opnes? Maybe that's what they're refering to. It still doesn't explain why they blew the TARDIS up in the first place?

Yeah I think if they did blow up the TARDIS they must somehow be invulnerable to the end of the universe lol. Maybe they're extra-dimensional or out of phase or some sci-fi technobabble. Or they want the end of the universe because they hate existence (like the timelords in The End of Time).

Perhaps the universe wasn't looking at them, so forgot they were there.

The only true way to get Silence to Fall is to destory everything