Correct, with a lot of Spurs best players missing a massive amount of games. They were near the top of the table until that all happened.
Doesn't matter
They won the games. There's no luck to it.
The things you mentioned do not. The things that do make them miles ahead are:
Owner who spends money on great players.
Better manager.
Better squad with far more quality and depth.
Just look at how Arsenal fans and Spurs fans think about their own players in the aftermath of a loss and you'll find the answer you're looking for.
Injuries are part of football and so is building a squad deep enough to contend with injuries while playing in multiple competitions. I'd argue Spurs failed at that last year. Remains to be seen how their new squad does, which relates to the bolded. That's new this year, and all told, they've thus far added one player to their squad for next year, two if you count N'Koudou. Meanwhile, they've lost two, and there are rumors swirling around Trippier, Aurier, Alderweireld, and, kinda, Eriksen. Honestly, if Eriksen is sold, it doesn't take much to say that they've gone backward since last year.
For what it's worth, it's certainly arguable that Aubameyang and Lacazette are "great" players.
Regarding the underlined, even if that's all true, it's marginal at best, given that they, again, managed to edge out Arsenal by one point.
It's quite psychotic because this reaction only exists when other people are talking about their team. After the Europa League final they were agreeing with basically everything that's been said so far, but two months have passed while they've done nothing and their rival signed a world class midfielder, and now the teams are the same? It's very Evertonian of them and it's strange because Arsenal supporters used to be the most rational I knew of.
Look at the reaction from both sets of supporters after their respective European finals and tell me that those teams are of similar quality. One group was crying about their team having no quality or money and the other took stock of the future, the manager they have guiding them to a game of that importance, and how the team as currently structured could improve.
I see where the miscommunication lies. There's a difference between saying the teams are the same and saying that they're miles apart. I have no issue saying that Spurs are slightly ahead of Arsenal right now. I think Arsenal is still a year away from bottoming out and bouncing back while Spurs are on the upswing, although that could change with the defense of their squad starting to disperse.
Chelsea finished one point ahead of Spurs and I think most level headed fans would also suggest that Tottenham is considerably better thank Chelsea too, despite the final standings last season.
Well, losing Hazard and a manager while in a transfer ban might have something to do with that. Let's not act like that isn't a major reason why. Now, we can say that N'Dombele is worth however many points we want, but I don't think it's questionable in the slightest that he's not as good or impactful as Hazard.