LSD has been consumed in hacker circles for decades, especially Silicon valley - 60s and 70s were both time when LSD was widespread and software world started heating up.
And since hackers are intellectually curious, LSD is quite an attractive drug. Pretty simple.
For anyone interested in exploring this history in depth, I can warmly recommend Fred Turner’s book From Counterculture to Cyberculture: Stewart Brand, the Whole Earth Network, and the Rise of Digital Utopianism. Very interesting stuff.
The Whole Earth stuff is fascinating. If you can get hold of the Catalogues they're full of interesting details.
People may want to read The Cuckoo's Egg (Cliff Stoll) and The Eudaemonic Pie (sometimes called The Newtonion Casino in other countries) to get the flavour if this bit of history.