Language change is weird, man

My SG book is teaching me the paradigm for the verb ‘to be’ today, and I was noticing the personal pronouns, which are as follows:
I- mi
you- thu
he/she- e/si
we- sinn
y’all- sibh
they- iad
you(f)- sibh
I though it was funny that the singular pronouns are so very similar to their English equivalents, but the plurals are way off base, and I was curious if English plural pronouns somehow got changed from Germanic roots to Romance roots. So I compared other Indo-European pronouns. And this is where it gets really strange. Observe:
German French Italian Spanish Danish
Ich je io yo jeg
du tu tu tu du
er/sie il/elle egli/elle el/ella han/hur
wir nous noi nosotras vi
sie ils essi ellos de
ihr vous voi vosotras I
Sie illes lei ellos de

You might notice that you singular is very similar all the way across the board. Makes sense, they’re all from the same family. But everything else goes crazy.

English and German use similar first person singular pronouns (ich and I), while SG randomly uses what sounds like the English and German first person accusative. French, Italian, and Spanish are quite similar, as you’d expect. But Danish (a Germanic language) uses something very close to theirs. Where did that come from?

And third person all seems totally normal; with Eng, Ger, and SG all very similar while Fr, It, and Sp are grouping up with a totally different set of sounds. And then Danish plays the wild card, pulling out the third person accusative for it’s nominative case.

For first person plural there’s we/wir/wi for Eng/Ger/Dan and nous/noi/nosotras for Fr/It/Sp. The Spanish is a little strange, but not too bad, all in all it’s about what you’s expect. But SG has sinn, which comes out of nowhere. That’s not even similar to another case, it’s just completely new.

Second person plural has everybody just about back to normal (English doesn’t count, since we don’t really have one, and Danish is a bit strange, but I can see where it might have come from). But English gets to be the odd one out in he third person, they doesn’t sound anything like the others.

And then you plural happens, and everyone across the board just borrows their plural you except Italian, which seems to be using some variant of second person singular.

I’m really curious why it is that every single pronoun group has one member of the language family that just does something seemingly completely random, except second person singular. What is it about that particular pronoun that keeps it so regular? And why a different oddball in every case? Why isn’t it Danish that’s just always a little weird? I imagine my sample size is just too small, but it makes for a very strange pattern. Anybody know what’s going on?