Secondly, the later 'thou shalt not use tables' edict from the sort of people who actually joined the relevant W3C committees came after a few years of ubiquitous table use due to the limitations of CSS, but more importantly several years before Flexbox and Grid were even draft specs [other unsuccessful drafts existed]. People used tables because CSS wasn't good at the sort of layout they wanted to achieve, and in response W3C members... told them that tables were evil to screenreaders and they should suck it up and use hacks for at least the next decade
Arguably floats weren't well designed anyway (floating an image inside a box was all kinds of trouble except in IE which disregarded the spec's insistence it was supposed to overhang the bottom) but there was already a case for a proper grid and even that's comparatively minor compared with the 13 year gap before the draft spec for the next gen layout syntax.
This does not match my recollections of CSS in the mid 90s.
My recollection is that people in general just laid out a document like you'd lay out a word document, and as such the minimal amount of floating that people did was not that difficult.
I recall a) when table-based layouts became very popular, and b) when they became very unpopular and we had to start doing all kinds of funky things with float to avoid them.
But returning to the birth of CSS if all you want to do is to put an image in a word processor do and have the text wrap around it, float is not too bad. If you want to design a layout system around it, it sucks.
So, like, to understand "why floats" in a historical sense, it's important to understand that the kind of layouts that tables (and yeesh, I can't even remember what they were called... frames maybe) were used to achieve didn't exist when CSS was first being used...
it was more like the generic tools in a basic rich text editor.