There's a handful of notes on this going "well fuck you, do you know how hard it is to BE the speaker and not have anyone greet you?" and uh, yes, yes I do, because I did those stupid ass soft skills/resilience/insert other assorted nonsense workshops for schools for a living for a while, and I still agree with this.
The key to being an effective speaker is the ability to understand your audience. You need to understand people in order to build a rapport with them. And you need to build a rapport with them in order to effectively guide them from where they are, to where you need them to be.
So. Here is the situation from the perspective of the audience: this random person, whom they have never met before and do not care about, is being paid by employers/school powers that be to come speak on a thing. In other words, the speaker is the one benefitting from being there. Meanwhile, the audience has likely been ordered to be there, for no immediate, tangible benefit in return. It is early in the morning, they are sleep-deprived and under-caffeinated, they have a shit ton of stuff on their to-do list, they are unconvinced whatever the speaker is going to say is going to be of any use or relevance whatsoever, and so they see this talk as a waste of time that they could instead be spending on sleep or at least finishing off things that are actually necessary for work/school. And now this rando, whom I repeat, is supposed to be the service provider, whose presence is already a pain, is asking for even more effort on the audience's part by asking them to smile and be chipper. All before saying a single other word that might convince said audience that they are going to get any benefit whatsoever out of being there. Fuck that.
You gotta understand, you are not some rock star that people are already invested in and actively want to see. Those get to do the "scream! I can't hear you! LOUDER!" thing. The fact of the matter is, you are probably someone your audience has no interest in seeing, and until you give them a reason for wanting to be there, you cannot ask them for even more emotional effort. That's not going to endear them to you.
I am by no means a particularly great speaker, but I can tell you now that I have gotten far more immediate rapport and engagement by simply going "hello hello, morning, how is everyone?" and then when I get the predictably unenthusiastic mass groaning and grumbling, and unenergetic "morning"s back in return, replying "heh, big mood. It's final project season innit; how sleep deprived are y'all? --yeouch, intense, well I'll try my best to keep this as painless as I possibly can; I'm here today to talk about--" etc etc. Simple, sympathetic, and while it's not the most energetic and enthusiastic thing in the world, it puts me on "their" side and opens a connection that I can build on for the rest of the talk, instead of instantly making my audience feel 10x more tired and hostile.
If you are not a speaker being paid to be there, but are instead someone giving a presentation for an assignment or presenting a paper or whatever, then I've found that being sincere and a little self-deprecating, possibly just a tiny bit vulnerable works pretty well: "Oh god, so full disclosure, I don't speak very often and I'm sweating bullets right now, and also I tend to babble like a bullet train when I'm nervous so if at any point you cannot understand me please ask me to slow down, but I have a thing I need to present, and I think it's pretty cool, and hopefully you do too." Your audience has probably been in your shoes before, and are now inclined to be nice to you out of sympathy.
In both cases, it's about understanding your listeners and where you stand in relation to them and using that to build that initial connection. You cannot demand connection; it never fucking works.
