Sovereign-class Enterprise didn't get built overnight.
It's likely they already had one ready and just simple renamed it Enterprise when the -D was destroyed and reassigned the -D's crew to the new E.
Don't forget that Riker was in command of the
Enterprise-D when it was destroyed, and losing the Federation flagship to a 20-year-old Klingon Bird of Prey when it could so easily have been avoided by simply ejecting the Warp Core must be a little embarrassing. It's a wonder he wasn't drummed out of Starfleet for incompetence, never mind not being offered his own command.
Very true. I imagine that he and Picard were both court-martialed.
As to the question on why Riker put off commanding his ship for such a long time, I don't know if there is a good reason. When he was first presented in TNG, he was an ambitious officer, eager to rise through the ranks. It's understandable that he turned down the Drake to be the XO on the Federation's flagship, the Enterprise. Maybe even turning down the Ares makes some sense since he was only two years on the Enterprise. After that, though, by the time of BOBW, it really doesn't. Unlike Spock, who never was interested in commanding a starship, Riker was on the command track. His lack of ambition in the later seasons of TNG just didn't ever make much sense at all. In fact, as we heard from that admiral in BOBW, it was hurting his career.
The loss of the Enterprise in GEN, however, could very well be a big ding on Riker's record. The Federation's flagship was taken out by an antique Bird of Prey that it vastly outgunned on Riker's watch, all because Geordi's VISOR was compromised, something that happened before on TNG. Riker, and maybe Picard (for leaving the ship in Riker's hands), deserves some of the responsibility for that screw-up. That may have put him down further on the Captain's list for his first command, despite his laudable achievments, particularly wrt the Borg incursion in BOBW, perhaps Riker's finest TNG moment.
As for why Picard wasn't an Admiral, yes, there's what Kirk said to him, but I'm of the opinion that there's more to it than that. Remember, we saw that Picard never made Admiral in the possible future of All Good Things, where the events of GEN apparently never happened. That implies that there could very well be other reasons he never was promoted. I'm of the opinion that his experiences with the Borg ruined his chances at promotion. We know that SF was nervous about Picard after BOBW from Admiral Satie's reaction to him in Drumhead and the admiralty asking the Ent-E to stay away from Earth in FC. Then there's Picard deciding not to use Geordi and Data's computer virus against the Borg in I, Borg. That decision, to me, was inconceivable for Picard. In the end, SF's biggest mission is to protect the Federation from its enemies, and there is no enemy as implacable and dangerous as the Borg. The correct decision was to use the weapon and Picard put his principles ahead of his duty as a SF officer. Janeway (both Captain and Admiral) ultimately made the correct decision in Endgame. Even William Adama tried to take out the cylons in BSG with a plague. Finally, Sisko put his personal principles on hold in the great DS9 episode," In the Pale Moonlight." Adama and Sisko didn't feel good about those decisions, but they knew it was the only thing they could do (Janeway didn't look like she had any moral misgivings, which was disturbing seeing as how she knew from direct experience that the Borg drones were victims). We saw how Picard's decision not to use the virus angered Admiral Nacheyev in Descent and Picard finds himself questioning his decision. In the end, he chose Borg lives over the lives of Federation citizens who were murdered by the freed Borg at the behest of Lore. Based on those considerations, I think Picard has some enemies in the Admiralty. He still apparently had enough clout and friends though to get command of the Ent-E, but maybe they've made it plain to him that he'll never again be offered the rank of Admiral, due to security concerns and the dings on his record from I Borg and the loss of the Ent-D. Not that Picard cares that much. He clearly enjoys being a starship captain and we've seen that, unlike Kirk, who was obsessed with commanding the Eneterprise, he's capable of moving on to other projects and interests.
(i think there is anovel or two with the F and Picard was serving as CO for a while)
