In Kira`s case, he would need to use internet on his favor......now, thinking like a villain/well intentioned extremist....this is what would i do if i were Kira vs the internet.
step 1. start using public computers for Kira related researches. Any plan discussions would be on private discords and communicated in code.
step 2:Kira, instead of being one person would be an anonymous-esque group where Light and his supporters kill and cover each other`s tracks.
step 3: I would pretend to chase Kira and fake my own death. (they cant suspect a dead person, i can quit social media without rising flags and i can be Kira full time).
step4: i would take about 75% of the pages of the real death note and scatter them around the word with fake death notes. (i would carry the real one)
all "kiras" will transport fake deathnotes with some with real pages around the world. It is a weapon that is too easy to conceal on an airport and to send by mail. Everyone will have a randomized list of criminals to write about. The ones with the real one will see Ryuk, but will forget as soon as they pass it to someone else. . The fake Kiras with the real death note may temporarilly believe they are Kira).
aditional benefit: some of the kiras would accept the deal to get the shinigami eyes. Those can add further to the list of criminals to excecute and to take down some police/fbi members chasing Kira.
step5: gain popularity by killing unpopular corrupt figures like Kim-Jon-Un among others. Use this to liberate countries, gain their support and take power, chosing honest rulers for these countries and taking down corrupt and sleazy ones.
step6: propaganda. Slowly start manipulating the media, until the internet becomes your ally instead of foe.
step7: always rule from the shadows. Kira is a divine figure after all and his voice is heard by his chosen representants.
step8: Kira will name all the future generations, as a "baptize rite" or something akin to have an absolute control on who lives and who dies. Also, the team would track down other death notes to monopolize the power of death.
of course i would not publish this on Tapas as part of my plan XD