I cannot find data for February 21. How do you account for the decline and then increase? You had said the curve was already dropping rapidly. Why was it dropping? hedrick says seasonality. Possibly so.
Not just weather. There are several things going on. There was nationally a peak for holidays. This is quite understandable, since people gathered together. It was also cold, though the peak looks to be more timed for the holidays than the minimum temperature. We're now in a period when there was a decrease after the holidays. The exact timing seems to differ from region to region, but the whole US saw both the rise and the fall.
Second, we have warmer weather. I don't know how much that impacts the virus spread directly, and how much the effect results from people doing more outside, which is safer, but the relationship seems obvious.
Third, vaccination is presumably beginning to be enough to have some effect.
In the other direction, every state, not just Texas, has relaxed constraints. Not the same, in part because the constraints had been different.
Also in the other direction, we have variants that are known to spread more rapidly than the original Covid. They seem to be higher in Texas than many other states. Also in NJ (and presumably all of metro NYC). Projections are that the B 1.1.7 variant is going to increase rapidly. That's the main reason NJ is worried.
Both of these last things are probably what's driving the nation-wide increase of the virus. Changes don't happen at the same time in all states, but there's at least some sign that Texas is starting to see the increase as well.
I assume that the latest peak won't be as large as previous ones, because of the combination of warming and vaccinations. But if everyone starts behaving as they did in 2019, more people will get Covid. I'm not convinced we have very good models, but you can look at one worst-case model at
IHME | COVID-19 Projections.
How much care is it worth to avoid what could be 50,000 deaths? That's a personal judgement. Maybe it's not worth all of us continuing to be careful. My own state (NJ) has loosened up some, but still has some capacity restrictions on restaurants and other types of gathering, and a mask mandate.