ALl stuff that happend with Walz 30 years ago and he has been, as far as we know, stone cold sober since. Hegseth has multiple recent reports about heavy drinking.
They are not anonymous. The Senate has names, those names just aren't being released to the public. This was referenced numerous times during the hearing whenever Hegseth would try to hide behind that weak shield. This guy's own mother wrote an email castigating him for abusing women, he promised multiple REPUBLICAN Senators he wouldn't drink if he was confirmed. Because this doesn't match with some people's political leanings they're dismissing commonly used sourcing that they would readily accept if it matched their political leanings.
This guy was a relative nobody, a backbencher on Fox & Friends that just happened to match what Trump was looking for (young, good looking, etc) so he got the nod, and so we learned more about him and it's readily apparent he's unfit. It won't matter, he'll get confirmed because many of the Republicans Senators are cowards (although some, I'm sure, are fine with this).
Here's the part, it's all about "pissing off the libs." Hegseth isn't "special." There are dozens of guys that could enact the same policies Trump wants that don't have multiple reports about public intoxication, that weren't fired from two Veteran's organizations at least partially for drinking, that weren't accused of sexual assault, that don't have multiple women restricted from commenting by NDAs, etc. They could have gone for any of them, and had a ho hum confirmation. But Trump and his team want to flex and see who will be "loyal". And so the Rs will cower. Maybe they'll have some backbone over a legitimately dangerous person like Gabbard or Kennedy, but just for that whole laundry list up there about Hegseth who's "just" unqualified? He'll sail thru.