During the pandemic, wealthy people have seen massive gains through huge increases in asset values without doing any work, too. Generally speaking, wealthy people have seen much larger increases in net worth during this pandemic than the working poor. Why is the problem with the economy poor people staying home on unemployment rather than monetary policies creating an asset bubble that the already well off primarily reap?

The actual problem is that despite all this money washing around, real wages for many people have not went up at all.

You're overestimating the generosity of unemployment benefits, and you're underestimating people's work ethic when given unrestricted (strings-free) transfers.

In the first instance, unemployment benefits do not typically replace "half to 3/4 of your salary," and under ordinary circumstances US benefits are greatly limited in duration. Those for whom the "half to 3/4 of salary" replacement is more correct are also those who started on the low end of the salary scale, and I daresay the working poor should not be the subject of your ire.

On the second point, your assumption -- while common enough -- has not been replicated in modern-day UBI trials. On the balance, those have shown somewhere between no change and small positive changes to work intention over the existing set of social benefits, which on one hand tend to require demonstrating job-search effort but on the other hand tend to be withdrawn beginning with a low earned salary level.

In particular, I have seen no modern-day research demonstrating that providing a fixed benefit creates an indolent class.

We (in the US, at least) are paying able bodied people not to work, precisely in order to have them not work. The policy being that it is better for the entire society if all the laid-off service economy people (retail, hospitality, entertainment, restaurants, etc.) stay home. If we did not pay them, they would find other work, which would require them to leave home. Which would be counter to the public health policies. Staying home is the _point_ of the policy, not a side-effect.

You don't lose UBI if you start working.

This is very important, because otherwise UBI would have the bad incentives of our current unemployment program. Avoiding those bad incentives is the entire point of the "U" in "UBI."