There are a LOT of reasons why Sailor Moon faded while Dragon Ball did not, but while Crystal didn't help, all things considered, it's a non factor in this regard.
The biggest reasons are that Dragon Ball was always bigger than Sailor Moon and that since Dragon Ball is a shonen property, it has longevity in terms of merchandising that Sailor Moon never would have had a chance at due to being a product aimed at girls. Even if Sailor Moon had been managed perfectly, it would never eclipse Dragon Ball simply because devotees aside (people who would buy Proplica products, for instance), boys products offer more avenues for revenue than girls products.
SailorSugarbabe brought up an important point. After the Sailor Moon anime ended there were opportunities to extend the franchise and the musicals were a success...in Japan. However, instead of working on a new animation that could be released internationally, in 2003, those in charge decided to go the cheap route and produce a low-cost live-action series. Like Teenage Mutant Ninja Turtles: The Next Mutation, this was a misfire. Even if you acknowledge there is some critical or artistic merit to PGSM, the fact that it is a Japanese live-action drama limits its appeal.
Another factor that is overlooked is that despite the fact that Sailor Moon was airing in the U.S. in 2000, after SuperS stopped airing it was dropped like a hot potato. Yes, there were the DVDs released, but without Sailor Moon on TV, there was nothing. By contrast Dragon Ball Z was airing first-run episodes for a few years afterward. Simply having more material means more opportunities to extend the franchise.
But there is also critical point which kept Dragon Ball alive both in the West and the east. Just when the Dragon Ball/Z episodes were about to go into reruns in the West and had stopped production in Japan for years, the franchise was kept alive in part by a very important tie-in product.
DBZ Budokai.
This was a Dragon Ball Z fighting game, which while very flawed, wasn't downright awful like some earlier games. And since most Dragon Ball video games did not come out North America, that this one did was the first time that a lot of American fans of the show actually played -- and thus it sold well in both North America and Japan. That means the kids who would have either outgrown Dragon Ball were kept in the fandom just a little longer because of a video game. There may be a chicken-and-egg problem in which a video game is only made because there is clearly some market for it
You know what happens when things sell well? They get sequels...which also sold well, and also had the benefit of being better games. Thus, while new animated content was next to nil during this period, the games became a surrogate. It didn't hurt that as a fighting game, it didn't just tap into the whole fighting theme of the series, but it essentially acted like a fan's playable fanfic. Gamers got into it and thus some got in to DBZ, but the main purpose of the games was that they helped keep interest among fans alive. There are other factors, of course, and a video game series is not the only reason why Dragon Ball Z stayed active, but it did play an important part.
Now by contrast let's see what Sailor Moon has done. Outside of the musicals and PGSM, the franchise was dormant, and even eventually the musicals stopped. So what is keeping Sailor Moon relevant in the interval years? Nothing. Franchises need new blood and new material or they die. Sailor Moon's only attempts at new material have been distinctively unexportable, Furthermore, TV shows and musicals have a much quicker expiration date than some forms of tie-in merchandise.
As has been mentioned, since Sailor Moon is Naoko Takeuchi's "baby" and she wields incredible executive control, then Toei's hands are tied to an extent, which is why they shift their focus into making PreCure a success. PreCure is theirs and thus they can develop it how they want and have the entries of the franchise evolve.
That's not to say Crystal couldn't have redeemed the franchise. As an animated product, if the animation were impeccable, a lot of the plot points introduced by the adaptation would be tolerated much better. However, Crystal didn't put the franchise into stasis. Toei did.