The whole finger poke of doom actuallyhad it's own topic postings last year, surprised to see it renewed. To understand the significance you have to remember where the wrestking war was at this time in jan 1999.
Hogan was mostly mia the last two months of 98 after his Halloween Havoc match vs Warrior. WCW used Kevin Nash's yr long undefeated streak as WWF Champ as part of the promotion heading into his Starrcade 98 title match vs Goldberg. GB's undefeated streak was the most talked about thing in wrestling and like him or not he was more popular at that time than any wrestler in either company not named Austin. The NWO had already split into two factions, a Nash lead WolfPac faction with a revolving door of WCW fan favs like Luger & Sting and the NWO Black & White, the Hogan Bischoff heel faction that mostly was filled with midcarders and enhancement talent other than Hogan & Scott Steiner. The whole NWO story was ridiculous at this point, the group not much of a factor although Bischoff maintained a strong heel presence on TV. During the Starrcade Main Event, Scott Hall, who longago had turned on Nash & sided with Black & White, interrferred and cost Goldberg the match. Lets not forget Goldberg won the title beating Hogan on Nitro before the whole NWO story went to crap.
Now you have potentially the biggets re-match since Hogan/Flair in Hogan & GB, not too mention Nash as champion being courted by the Black & White. Nash and Hogan has never taken place, the real battle for NWO control. Nash vs GB would have been huge since Nash was the only guy who actually beat him. Enter Ric Flair, red hot in his return from contract dispute and now not only wrestling but instilled as President of WCW. WCW fans were dying to see Flair finally go over Hogan. So much potential...
With the Finger Poke, WCW essentially re-estabaished Nash and Hogan as teammates, heels, and leaders of re-formed, leaner NWO purging most of the 2nd rate talent. Hogan again had the belt, Goldberg was hot on his trail, but WCW had a powerful ally in President Flair, finally a balance of power in the fued. WCW then burried Flair, coming up with a ridiculous story where is son is seduced by Torrie WIlson to cost him his PPV match vs Hogan (which has some great set up and drew the company's best buyrate all year). They also left Goldberg almost completely out of the main event scene, leaving him in midcard matches vs Scott Hall and other heels who didn't interest the fans. Goldberg Nash 2 eventually took place on the midcard of an off month spring PPV with no titles and little build up. Meanwhile, with the new lean mean NWO back and way over, WCW quickly split the group again for no reason, turning Hogan face and Flair heel almost out of nowhere to luke warm reaction from the fans, as it made almost no sense storyline wise.
Essentially the finger poke was a master stroke that reinvigorated the NWO as the lead heel force in the company and set up some terrific match and story potential. What WCW did afterwards actually made almost no sense. Nitro was topping 5.0 mark in ratings in Jan & Feb despite being in direct competition with RAW but by late April those numbers were dwindling fast. Even worse, the company was doing so well early in the year despite having Luger, Sting, and Brett Hart all on the shelve with various injuries. Imagine WWE topping 5.0 ratings in 1999 with The Rock, Foley, and Undertaker all out of action at the same time.
The Finger Poke didn't kill WCW but the what came afterwards, all the squandered potential, that was killed the company.