Why can Babidi/Dabura tell who's the most powerful/that there's enough ki amongst the seven? And why not kill Yakon?

[Warmmedown]

The Z fighters suppress their ki when hiding near Babidi's ship. So how does Babidi feel so confident that there's enough ki amongst them to revive Buu? Even if he has some magic way of knowing, how could Dabura know who the strongest three are? Do you think they felt their kis when they were flying towards the ship?

Also why does he send Yakon and PuiPui to collect energy from Vegeta/Gohan/Goku? Goku SSJ1 (initial vs Yakon) is 3000 kiri, Yakon is 800 kiri - do you think Yakon is less than 3x stronger than base Goku? Because if Yakon is over 3x stronger than base Goku, why not just have Dabura kill Yakon for energy instead (since he thinks the three base saiyans are enough energy to revive Buu)?

 

[SSJ2]

They can't sense ki given that they needed the Kiri meter to gauge Goku's power. Unless Babidi used the Kiri meter on his crystal ball when the Z Senshi were flying in from the Budokai, but this is never suggested. I honestly have no idea how to make sense of this part of the story given that the Z Senshi were all suppressed to 0.

 

[GreatSaiyaman123]

Probably magic/clairvoyance, since Babidi is sort of a wizard with a crystal ball and all. Dabra clearly uses magic too. So I think they foresaw it on the crystal ball, because they clearly can't sense Ki later as SSJ2 points out.

The Pui Pui and Yakon stuff? They're just plain stupid. They think SSJ2 Gohan's energy came from hundreds of humans (Gohan's at least hundreds of millions of humans) and when Pui Pui dies they're like "But we didn't see anything like that 300 years ago!" meaning they expected to take energy from guys like Roshi and Piccolo Daimao. They just knew someone was coming, but had no idea what they were going to deal with.

 

[SSJ2]

Probably magic/clairvoyance, since Babidi is sort of a wizard with a crystal ball and all. Dabra clearly uses magic too. So I think they foresaw it on the crystal ball, because they clearly can't sense Ki later as SSJ2 points out.

The Pui Pui and Yakon stuff? They're just plain stupid. They think SSJ2 Gohan's energy came from hundreds of humans (Gohan's at least hundreds of millions of humans) and when Pui Pui dies they're like "But we didn't see anything like that 300 years ago!" meaning they expected to take energy from guys like Roshi and Piccolo Daimao. They just knew someone was coming, but had no idea what they were going to deal with.

They explicitly state that they can gather good energy from the Z Senshi though. Makes no sense if they are assuming they will be Piccolo Daimao level at best.

 

[Warmmedown]

With the magic/clairvoyance, if they used that either to get a rough feel of the Z fighters' strength (and then used the kiri meter for a precise measure) or somehow used magic to just predict "we will get enough here" without any feeling of their power, why would he think Pui Pui can compete with Base Vegeta? I suppose he could be completely clueless about fighting and that PuiPui is weaker than Vegeta, but not realise how much the gap matters so he thinks that PuiPui can at least do some damage before he dies. That still takes assuming that he somehow knows that the saiyans will only fight 1 vs 1, which he never mentions.

Maybe the 300 years ago was the Nameless Namek? Three of him is still nowhere near enough though, if Buu was really only half-charged just prior to the Yakon fight, unless they have thousands of senzu beans.

 

[Kyo]

Kaboom I believe had an okay theory about this back in the day, where Babidi can tell that they have high latent energy, but doesn't believe that they can actually utilize it in combat. It still doesn't make much sense, but it's one of the only ways to somewhat reconcile the events of this part of the story, because Babidi's expectations for their combat ability makes no sense.