Oh, horse caca.
Ivan IV was not some sort slightly bloodthirsty social reformer--he issued the first laws in Russia restricting the movement of peasants, and the Oprichnina hit the peasants living there as hard as the nobles. So, no, he didn't JUST kill nobles. Ivan killed Russians. Poor Russians, rich Russians, noble Russians, common Russians.
As for increasing the power of his nation against foreigners--well, he did quite well in the beginning attacking the weakened hordes of Khiva and Astrakhan, back when he actually seemed to trust and work with those supposedly corrupt service nobles he just had to get rid of. But when he started turning against them and calling the shots, he got Russia involved in a lengthy war against all its western neighbors that dragged on for most of his reign and ended with Russia losing territory. Partially due to his constantly escalating the stakes, and partially due to his starting up that Oprichnina thing, which I have to stress was a horrible idea. So again, no not really, especially as not that long after his death, Russia is getting invaded by those nations it was fighting against not that long ago. (And hell, while he's alive, the Crimean Tatars are raiding Moscow. Yeah, brilliant success there.)
Let's move on to that 'western neighbors invading' issue. While part of what started the Time of Troubles was the whole dynastic failure issue--which can be landed squarely on Ivan's shoulders--another part would be that this was a society where bonds of trust had been eroded. And yep, that can also be blamed on Ivan, who did everything he could to foster suspicion and fear among his people. That was Ivan's legacy--not a stronger nation, but a nation weakened.
Now, returning to the opening question, why didn't people rise up against him? Well, it's complicated. The position of Grand Prince of Vladimir and Muscovy held a great deal of spiritual heft, something that Ivan exploited mercilessly. Further, Russia had just emerged from a troubled regency, and before that, a lengthy period of internal strife. Early on, there seems to have been a general feeling that strong rule was needed, and putting up with Ivan's oddities was just the price of that. Later on, Ivan had set up enough mechanisms to nip anything in the bud--and people probably didn't trust each other enough to start anything.
Oh, and as for Ivan being poisoned--he was a 54 year old man with numerous bad habits, among them heavy drinking. A stroke in those circumstances is hardly suspicious.
My apologies if this has gone on a bit, but Ivan apologetics rival Lost Causers in my mind in their efforts to make the evil seem acceptable.