For the case of Sandman and Lizard, not every villain was transported just because they died fighting Spider-Man. The idea that brought all the characters together on Earth-199999 was that they all knew Peter Parker was Spider-Man.

"That little spell that you botched where you wanted everyone to forget that Peter Parker is Spider-Man, it started pulling everyone that knows Peter Parker is Spider-Man, from every universe."

Speaking of everyone knowing, that is the exact reason Tom Hardy's Venom was as well. For while he doesn't have a Spider-Man of his own, the symbiote does know through the collective symbiote hive mind. Of which he shared the info with Eddie at the exact moment the spell broke.

I mean Sandman was still around

However it was said after he fell into the machine that turned him into Sandman, he was transported there

Curt went to jail, don't recall how he got transported

As for Eddie and Venom, they were transported at the end of Venom: Let There Be Carnage

Why he doesn't have a Spider-Man in his universe well due to the fact Marvel currently holds the rights to Spider-Man so there isn't a Spider-Man in Sony's Universe.

There will be Silk and Spider-Woman as replacements for Peter

What @Xandermcc said

@Optimusprimebumblebee "Neo Astral-X" 123 Flint was Sandman for a while before he got transported to MCU. He made his peace with Peter, like at the end of Spider-Man 3. So it was not right after he fell into the sand pit. Flint was even happy to see him when he realized it was Peter. He of course thinking it was his Peter.