No single organisation has control of the entire internet. Without trying to sound patronising, it is a complex intricately connected series of networks. The blacklists in question are run by Spamhaus, an organisation which exists to prevent spam on the internet. To answer your question, you probably did nothing to be there. Spamhaus runs a "Policy Blacklist" which lists most dynamic residential IP addresses, because they should not be being used to run mailservers. These blacklists SHOULD only be used for mail filtering, but sometimes mistakes happen, errors occur, or humans do dumb things.
It appears that somewhere between your ISP and the SLR servers, one of the transit nodes has been timing out.
@Rakly3 is speculating that the cause of this timeout may have been your IP being present on a blacklist. That might be correct, but in any case it's not something that anyone here can control.
Whilst I understand, and indeed share your frustration, SLR was not to blame. When the issue was brought to their attention they worked really hard to resolve the situation and to put mitigations in place so that today it "just worked" again.
SLR has control of their servers, they were working the whole time. I can confirm this because I forced an alternative route for myself using a VPN when I had the same issue last night. SLR does not control the Spamhaus blacklists. They do not control what other people do with those blacklists. They do not control every hop between your ISP and their server. They are categorically not at fault here.
It would not be reasonable to blame a local shop for stock issues when the Ever Given blocked the Suez Canal. It's not reasonable to blame SLR here, no matter how frustrating the issue was.