So, can someone explain what the glitch patch is and why it justifies a leaderboard wipe?

no more room 100 skip, fella tech and wire tech

Not entirely sure myself but I know that basically it patched some speedrun tech such as Wire Tech and that one Door 100 skip and Fella Tech which allowed for some time to be lost. To make it completely fair, they reset the leaderboards as you can't do these anymore. If they didn't then the top 5ish runs would stay there until another broken tech gets discovered :P

lots of tech was patched so getting record would be significantly harder