Vannevar is presented as a very powerful vampire, but his greatest strenghts are his allies. Nickolai, a russian Ventrue acting as his right hand, apparently had a bunch of sensitive information regarding very important kindred, and thanks to these secrets, the pair has managed to persuade Karsh into letting them stay in control of San Francisco. Other powerful allies of Vannevar were Benedict, the martial artist and Tremere primogen of San Francisco; Iwo, a japanese wizard of some sort; and Hortator - some kind of aztec warlock.
Vannevar Thomas and his domain of San Francisco were heavily featured in the novels Dark Prince and its sequel/prequel, Prince of the City; Thomas was actually the protagonist in the latter novel, which spans the city's history from the Gold Rush into the present day. The Beast Within, the first Vampire short story anthology, featured numerous stories set at least partially in San Francisco. These stories introduced an error in continuity, however, as some stories referenced Prince Vannevar Thomas while others named the city's prince as Jochen Van Nuys.
Several of these stories were reprinted in World of Darkness: Strange City, which attempted to reconcile this error by changing references to Jochen Van Nuys into references to Vannevar Thomas. However, in the Revised era, a different solution was found in San Francisco by Night, in which Van Nuys was revealed to have replaced Thomas' ineffective leadership of the city 1996, while he himself was in turn later replaced by Sara Anne Winder. The Beast Within Revised Edition retained the references to Van Nuys as prince that were found in the original versions of the stories, implying that those stories happened after Van Nuys' coup.
Vannevar most likely didn't survive the 1996 coup.