Sure, if Trump signs, rallies, caravans mean nothing. You're telling me a guy that barely gets 60 people at his speaking event will beat a guy that has upwards of 5 rallies per day with tens of thousands showing up to each one will spill-over crowds to boot?
Nope.
I've been doing well to allow my own life's experinces and my own eyes to paint reality for me... Polls won't change it and/or clearly bias media outlets won't do it.
without getting into the Trump/Biden issue specifically, rally sizes aren't a great way (especially now) to measure support. There are lots of diehards on the right who will show up at a rally and to vote. Those aren't the ones a candidate has to worry about. And a rally in OK isn't a great example of overall success since the electoral college makes some states matter more (as demographics currently stand).
Plus, there is a clear divide between people who believe in social distancing and those who do not. I know several hardcore lefties who have barely left their houses since march. They are ones who'd otherwise be at a biden (or other democrat) rally if they could. Trump's side doesn't seem to mind large events, so of course they will be larger.
I'm not saying you're expectations for outcome is right or wrong, just that rallies are like primaries and often attract dedicated individuals (regardless of party). It's the ones who can't or wont stand in line for hours to vote, or who will skip voting if it's hot/cold/raining or who think their candidate 'has it wrapped up' that can make a difference to a race (again, more down ticket than presidential, but still matter a lot in swing states).