26,000 is a lot, but with no other context it’s not an indicator of “crazy”.
As others have said: ammo is cheaper in bulk. It doesn’t “go bad” if stored properly, and you need different rounds for different guns. And for a while it was hard to find – you stocked up when you found it because you didn’t know when it was going to be available again.
1000 shells of 12 ga – that’s two cases, I have to drive a long way to find them, and I shoot trap every other week. 20ish shells, 12 ga slugs – left over from hunting I have 1050 rounds of 9mm, because I bought 3 cheap boxes of Blazer Brass on sale and that’s what I shoot at the range. 800ish of 7.62x54r – 2 spam cans, for the same reason. Probably 1500ish rounds of .22lr – 3 boxes of 500 rounds… same reason.
I’m not a nut, but if the cops raided my house the headline would be “found with over 4000 rounds of ammunition!!!”