Still, they did that at the request of the Speaker. They thought they could stop it on the floor of the House.
If they hadn't done what Speaker Howell probably indicated was in their best interests to do, they would probably not get a single bill for their constituents' interests passed for the rest of their terms. It's not nice to mess with the Speaker.
There's a very simple political arithmetic here. The GOP was getting increasing heat for the lack of a budget deal. Howell let the mavericks (not him and the no-new-taxes group) put their necks on the line to make a budget deal -- they're the ones that might get targeted for defeat by low-tax opponents in the next primaries. But he also knows that most of the districts have been drawn to be reliably Republican if they have Republican incumbents. If the deal goes through, the heat for not having a budget, and the potential real problems that engenders starting in May, go away, as does any minimal damage that the lack of a budget might have caused GOP candidates. So they no longer have to worry about the [small] possibility of actually losing control of the Assembly; lack of a budget will not be an issue that the Democrats could have run on. It's actually better for almost everybody; the moderates get credit in their more-moderate (NoVa) districts for getting the budget deal done, and the conservatives voted against it, so their constituents can't complain either.
That's why Howell permitted this to happen. The three guys who didn't show up for the meeting were just following orders. In fact, it was pretty astute politics by Howell to make those calculations and step in where it made a difference.