Alphabay was popular because it was easy to use, it was basically always up and had a huge user/vendor base. Let's consider the average Joe buyer for a moment (like myself). He just wants his weed and the occasional bag of blow without to many hassle involved. He has limited knowledge about the technicalities and is not really interested in learning more about it either. For the average joe, it's just about his weed and blow.
Markets like Agora and Alphabay always kept this in mind made it as easy as possible to trade. And with most people having only invested a small amount of money to buy a small amount of product this system was good enough, easy and if it all goes down you are only out a little amount of money, similar to having a dealer on the street delivering shitty product or cutting you short (money/product wise at least is what i am saying) - not the end of the world in most cases.
Now these high tech (HANSA) or low tech markets (Dream) have the potential to take spot one right? HANSA is still way too complicated and no average buyer will go through that and takes too much time for the average joe so it will never be the biggest market because most people are not willing to learn or unable too. They also closed registrations at the point most buyers dont know where to go, further diverting casual buyers. Dream on the other hand does not offer the same easy user experience Agora or Alphabay did and misses basic features and looks like a badly coded site.
So the first market that looks similar to Alphabay or Agora will take the crown. The average buyers don't wont to put up with either Dream or Hansa.
In the end, people just want to get high and most buyers don't care about FE, escrow multisig etc. As long as theres a pack a week in the mailbox all is good. And if it works 99 percent of the time and you lose once because of an exit scam, not exactly the end of the world in my humble opinion.
Not sure how hansa is complicated. Once you set up multi sig it's literally press buy and send coin to an address.