There is currently a bill proposed to do that (for stocks, not prediction market betting, but eh it's a start): https://www.govtrack.us/congress/bills/119/hr5106

It currently has 99 Democratic sponsors and 31 Republican sponsors (note: there are more Republicans than Democrats in the House). It will probably not make it out of committee. 2 of the 4 Democrats on the committee have sponsored it; 0 of the 8 Republicans have.

You need to apply it to staff as well and also the judicial branch and all of their staff. Then to all of their family as well.

The way I understand insider trading is usually prosecuted is you find out who made the bet & then you have to track down their communications to see if they got tipped off.

I'm sure every POTUS has at one point thought it would be great if they could dictate what congress does

Reasons to treat these situations differently:

1. The executive is doing very obvious insider trading, you can point at exact trades and bets that are clearly being made based on inside info. That's very different than the statistical arguments made about congressional portfolios.

2. Congress isn't privy to the same kind of inside info. Congress will know about changes in government spending with a few weeks to a month or so of lead time. The executive insiders were timing trades down, literally, to the minutes before the start of military action.

Basically that's a terrible whataboutist game you're playing.