I seem to recall it happening quite a few times in the past, though I would agree that bitcoin usually leads the way.

The thing with the altcoin market is that (IMO) it was due for some recovery this year, but the coronavirus outbreak just kind of messed a lot of markets up and that recovery didn't come as quickly as I figured it would.  The real question in my mind is whether this is going to be the start of a long-term trend, or if it's just a small rally that's going to be followed by more losses.  It's not as though the economy has even started to bounce back yet, and I don't think a lot of investors want to be putting their money in super-risky assets like altcoins (or even bitcoin for that matter).