Because during bullrun many investors are active to invest and join the ride of increasing price. Often, newbies who don't have idea of what they're getting into are the ones falling to invest in new projects thinking it's a wise decision, not knowing the risk.
But a good project doesn't mind to come out regardless of the market situation because they can survive if their project is solid and has a real use case. It's just that, during bearish season it is quite risky to launch a project since the market is struggling and many investors are afraid to invest.
That's mainly because they do not know what to buy and listen to fools. I mean if you have 700k followers on twitter, a newbie sees that and thinks that you are a famous person, and they look at the replies and there are so many people who ends up getting a ton of good feedback as well, like people loving that influencer and thanking him and all that.
This in return that newbie starts to think if he starts following that influencer and buy what he suggests, he will make a lot of return as well but that's not the truth. The reality is that the influencers promotes whoever pays him, and then the project could turn out to be nothing at all and go down a lot.
That's the sad truth, influencers are getting paid and they don't care what they are endorsing so long they have money.
Ask them the fundamentals and for sure they don't know what to answer about this aspect.
People should do their homework and assess the project itself, no one will do the work for them.
Most of the alts are only here for short-term. Once their pockets are full, they will abandon their projects.