Most of the users of bidbots claim that they do so because they want visibility for their posts
Maybe most users of bidbots claim this but I believe the vast majority of bidbot users do it for profit. Why? Because if you want visibility on the trending page, you need to spend at least 100SBD on bidbots. There aren't that many users who spend that much. Most bidbot users spend much much less. So why bother spending less if it doesn't give you any visibility? The answer must be profit.
The criteria for a post to appear on the trending page should be adjusted.
I agree. This won't eliminate the use of bidbots but maybe it will reduce spending big money on bidbots.
The number of human upvotes not the worth of the upvotes, should also be a factor for a post to be on the trending page.
There are bidbots where the actual voting comes from human accounts. For example, I pay 50SBD to the bidbot and I will get maybe 20-30 votes instead of 1 big vote from the bidbot itself. But your proposal would still be better than the current situation.